Perhaps your problem could be the same at this ?:

http://forums.b2evolution.net/viewtopic.php?t=23089

L

Thanks for the tip Iturner but my server is supporting PHP 5.3

The weirdest of this problem is that administration works fine, blogs work fine too, but can't see blogs when logged in!

Check error logs. You can also enable error reporting in /conf/_advanced.php

Uncomment both ini_set() calls in the top of the file. One for memory increase, and another for error reporting.

Thanks sam but I don't have the mentionned ini_set() call in the top of the _advanced.php file :(

on the error logs front we have interesting stuff following my IP and more precisely

PHP Notice: Undefined variable: classname in /inc/_core/_class5.funcs.php on line 87

and also some

[warn] Cannot get media type from 'x-mapp-php5'

PHP Notice: Undefined variable: classname in /inc/_core/_class5.funcs.php on line 87

You are using an outdated/unsupported plugin. Try to disable all third-party plugins.

[warn] Cannot get media type from 'x-mapp-php5'

Do you have Wordpress installed? If so, you should check with their support.

Plugins that the ones I have

Auto Links
Auto P
BB code
Ping de b2evolution.net
Plugin Ping-O-Matic
Plugin Twitter
Quick Tags
Smilies
Texturize
TinyMCE
Video Plug
Widget Archives
Widget Calendrier
Widget Who's on line?
Wiki Links

Found another weird message in error_log
PHP Warning: Missing argument 2 for load_class(), called in /var/www/vhosts/domain.com/httpdocs/skins/_toolbar.inc.php on line 45 and defined in /var/www/vhosts/domain.com/httpdocs/inc/_core/_class5.funcs.php on line 84, referer: http://www.domain.com/htsrv/login.php?redirect_to=%2Findex.php%3Fblog%3D11

[warn] Cannot get media type from 'x-mapp-php5'

Do you have Wordpress installed? If so, you should check with their support.[/quote]

No I don't. Only BE2EVO in that directory

Have you copied/saved any files from v3 to the new system?

sam2kb wrote:

Have you copied/saved any files from v3 to the new system?

directories conf, media and skins only

That's the problem. You should only copy third-party skins, not the whole directory, and only one file from /conf directory:

/media/
/conf/_basic_config.php
/skins/third-party-skin/

Just save your custom skins and upload all b2evo 4.1.2 files over again.

Yeaaaahhhh Sam you're da best! Works like a charm now!