I really hope someone can help me with this upgrade issue because I'm about ready to throw in the towel on it. I've got a 1.10.2 b2evolution installation that I just upgraded to 5.0.8. I did the upgrade on my local machine and then exported the db to my webhost where I imported it from the command line into an empty db. The upgrade went smoothly and I can access the backend, but I simply cannot get stub files to work properly. The selected skin displays for each of the stubbed sections of the site, but there is no content. At the top of the page, inside where the content should be, it says:

404 Not Found
b2evolution cannot resolve the requested URL.

I'm attaching all the info that seems relevant to the issue. I have already read all available forum posts that have anything to do with stubfiles, but unfortunately the information here is so fragmented that it's very difficult to try to figure out solutions to situations like this without asking directly. So, here is what I have:

The current (b2evo 5.0.8) .htaccess file:

# Apache configuration for b2evolution's base folder
# Lines starting with # are comments.
# Updated 2013-07-16

# PHP / SECURITY:
<IfModule mod_php5.c>
        # On some overly "secured" systems, the following may need to be added in each folder:
        # AddHandler application/x-httpd-php5 .php
        
        # The following will try to configure PHP in the way b2evolution would like it to be:
        php_flag register_globals Off
        php_flag display_errors On
        php_value error_reporting E_ALL
        
        # You may also need some of the following:
        # Increase memory limit
        # php_value memory_limit 256M
</IfModule>

# DISABLE LISTING FILES ON SERVER:
# Don't show directory contents (not desirable, especially for media folders)
Options -Indexes
# Note: if you have access to the command line of your server, it would probably
# be even better to type this:  a2dismod autoindex
# (This disables the directory listing module completely)

# DEFAULT DOCUMENT TO DISPLAY:
# In case no specific file is requested, we want to fall back to index.php
# In case some subdirectories are accessed, we want to display index.html
<IfModule mod_dir.c>
        DirectoryIndex index.php index.html
</IfModule>

# CLEAN URLS:
# The following will ensure you can pass extra params after the filename on the URL
AcceptPathInfo  On

# CATCH EVERYTHING INTO B2EVO: (even if no php file appears in the URL)
# The following will allow you to have a blog running right off the site root,
# using index.php as a stub but not showing it in the URLs.
# This will add support for URLs like:  http://example.com/2006/08/29/post-title
<IfModule mod_rewrite.c>
        RewriteEngine On

        # This line may be needed or not.
        # enabling this would prevent running in a subdir like /blog/index.php
        # RewriteBase /

        # Redirect any .htm .html or no-extension-file that's not an existing file or directory to index.php:
        RewriteCond %{REQUEST_FILENAME} !-d
        RewriteCond %{REQUEST_FILENAME} !-f
        RewriteRule ^[^.]+(\.(html|htm))?$ index.php [L]
</IfModule>

# If the subject/extrapath does not match an existing file, call b2evo!
RewriteCond %{REQUEST_FILENAME} !-s
RewriteRule ^(search|main|projectblog|acura_itx)(/.*)?$  $1.php

Here is the stubfile for that blog, with comments removed:

<?php
$blog = 3;
$show_statuses = array();
$linkblog_cat = '';
$linkblog_catsel = array( );
$timestamp_min = '';
$timestamp_max = 'now';
require_once dirname(__FILE__).'/conf/_config.php';
require $inc_path.'_blog_main.inc.php';
?>

Here are 4 screenshots: http://imgur.com/a/vtUKb

Screen #1 is the old b2evo 1.10.2 backend showing one of the blogs on the site, as it was set up for stub files and worked properly. I was always able to access the blogs by domain.com/stubname/2000/01/05/title_of_the_post

Screens #2 and #3 show the new b2evo 5.0.8 showing the same blog on the site, as it was set up for stub files. To me it seems as though everything is configured properly, but the site will not display any content.

Screen #4 shows the 404 Error and a few other interesting things. First, the address bar shows the /projectblog/ URL which appears to be using the stub, but the Top Menu shows "darksighed" in bold, as though it were the active blog instead. I don't know yet if this is significant because I don't know how this skin was updated for the latest versions, but my original design of that skin bolded the active blog, so that may be significant.

At this point I've tried everything I can think of but I simply cannot get this blog to work properly after the update. It's the same host, same hosting account, same everything.. mysql update went smoothly.. blog upgrade said it went smoothly... Maybe a permissions issue somewhere? Trying to determine if suggestions on these forums are still relevant when troubleshooting often creates more problems, and I've already implemented and then backtracked more than a dozen "solutions", so I really just need a step by step walk-through for this, relevant to the latest b2evo release, because stubs are just not working after the upgrade.

(A separate issue seems to be that stubfiles can no longer be named with underscores "_" in the filename.. One of the blogs on my site used an underscore which was also shown in the URL as /acura_itx/ and this is how google has picked up that url.. Is that still possible after this upgrade? I realize first things first, let's just get the stubs working to begin with, but that's another question I have.)

EDIT: On further testing, I've found that the skin for each stub is NOT showing after all. What I was seeing was the skin that was selected for the main blog of the site. None of the stubbed blogs show their selected skins, or content. Only the skin selected for the main blog shows. As soon as a stubbed blog is clicked, it gives the 404 Error, and the skin does not change.

EDIT 2: In Content > Blogname > Posts (for all the stubbed blogs), I'm getting the following error on the right side:
Notice: Trying to get property of non-object in /path/to/accountname/public_html/blog/inc/generic/model/_genericcategorycache.class.php on line 266

jj.