My b2evolution Version: Not Entered

Hi, I recently installed B2Evolution to my site.

I followed the installation instructions. I searched for posts regarding my problem with no luck. So now I post this question:

I get the error "No input file specified." when I try and add a comment to my test post. Also, the error will appear when I try and expand a "more separator" post. The postings seem to take a few minutes to process too. Anyone know how to fix this? Does anyone know what this problem is?

Thanks in advance.

J