I was going to suggest going to Edit/Preferences/Folders/Plug-ins and make sure there is a link there to your plugins folder.There should be 2 if you install Gimp-2.6.11 or Gimp-2.7.3 versions.
One should be through your program folder directory, and one should be through your user directory ie... C:/Documents and Settings/username/gimp-2.6/plugins
Yes, there are 2 just as you are stating it should be.
I doubt it is a DLL problem or path problem as Gimp would throw errors left and right on load.
You can try this.....Go to Filters/Distort/Wind and just keep the default settings and click ok.You have to have an image open to do this.And the image must be in RGB mode Image/Mode/RGB.
Just to see if you can use filters.
After messing with a good bit of the filters, the only one that worked was the lighting one. However, it took it forever to work.
I would also like to know if Windows/dockable dialogs/ select error console to see if it opens.
If it does dock it or just leave it open , go to edit/preferences/window management/save windows on exit, select save window positions now, and now close Gimp.
Now restart Gimp and see if any error messages appear in the console.I doubt there will be any but it can't hurt to try.Gimp can usually tell you what is wrong with it.
No, just as you thought, there were no errors within the box.