Constant Fatal errors – please help

Hi, I recently installed wp to transfer my old website over to. I had great success at first and everything was working great.

I installed a plubin for writing forms (i cant remember which) and since then i kept getting fatal errors. First it was one which said there wasn’t enough memoery, so i followed some other members advice and increase the limit in one of the files. That appeared to work for that error however then i kept getting errors like this: Fatal error: Call to a member function main() on a non-object…

So i deleted everything in the wordpress folder and started a new install. Now i am still hetting the same problem. This is the latest one:

Fatal error: Call to a member function main() on a non-object in /home/atvwa/public_html/wordpress/wp-includes/functions.php on line 779

I am at my whits end, luckily i still have the old site running. I must say this isn’t giving me great confidence in wordpress, if one simple plugin can cause this much trouble.

Please help, i love the idea of wordpress, but it is seeming to me to be a bit buggy.