This is a stretch but hopefully someone has an idea of what's going on here.
I was working on adding a feature to an extension (Amasty Product Grid Editor) to add the in stock status to the grid and allow in-line editing.
I ultimately got this working, but in the process something odd happened. I now have a problem with a completely unrelated extension (AheadWorks Facebook Integrator).
If the FB extension is enabled, I get almost no output in the browser on any page in the frontend or backend EXCEPT on the product grid in the admin.
On every other page it renders some of the header but bails after it tries to instantiate an instance of the FB Integrator helper class.
It throws this error:
Fatal error: Class 'AW_FBIntegrator_Helper_Data' not found in /var/www/vps_local_5/app/Mage.php on line 520
However, this file is there and all permissions are correct. The only thing I can figure is that in my failed attempts to get the feature added to the product grid I screwed up the database or something, but I have no idea what would cause it to think that a class file isn't there when it really IS.
The site works fine otherwise if I disable the FB extension. If I disable or even revert my changes to the Product Grid extension it still doesn't work, so it's not a conflict either.
I am leaning towards database only because after I got the changes to the Product Grid extension working correctly on my local dev server I copied those files to our remote dev server and it works great with no issues or conflicts with the FB extension.
So I have to believe that it was something in my iterations that broke something but I'm at a loss as to what.
Any ideas?