Welcome to Gimp Chat boop.
When you install Gimp-2.8 it uses the same GIMP-2 folder
This folder is located in your USERFOLDER
ie... documents and settings/USERFOLDER/gimp-2.6/ sub directories here
Inside this gimp-2.6 folder is a set of rc files ... gimprc, gtkrc, and others.
Remove or delete this folder (gimp-2.6) , and restart gimp-2.6.12
This resets all your files to first load restart.
That should fix it.
For now on be sure and use the NEW gimp-2.6 folder that will be created inside your USERFOLDER to collect resources. ie.. put brushes, scripts and plug-ins there NOT in the PROGRAMS/gimp-2.6 directory.
Let me know if that helps.