I opened up VS 2008 the other day and noticed that there were multiple instances of the same toolbox item listed (e.g. there were 4 Button controls listed). I tried to reset the Toolbox but nothing seemed to solve the problem.
The fix was to close VS and delete the 4 *.tbd files located @ C:\Documents and Settings\USER_NAME\Local Settings\Application Data\Microsoft\VisualStudio\9.0\ (under XP / Win2k3) or C:\Users\USER_NAME\AppData\Local\Microsoft\VisualStudio\9.0\ (under Vista / Win2k8 / Win7)
Upon restarting VS seems to rebuild these files and fixed the issue. Not sure why this happened and seems nobody else does either.