Is it possible that Norton Antivirus deleted a file from /usr/? I suspect that there is something going with a dotfolder in MyDocs and not anything on the rootfs. After all windows do not have access to the rootfs when connected as mass storage or otherwise. Even if you did manage to connect it, win wouldn't be able to read the ext partition.

Therefore a sane approach would be to run /usr/bin/controlpanel from terminal and see what errors it spews, then uninstall any app that adds a control panel applet (maybe it has corrupted settings and causes control panel to crash). Last resort before reflash is to remove all the dotfolders from MyDocs, except .documents, .pictures, .videos etc.