Some other things to try:
1. Compact the Default.gdb
2. Delete the geoprocessing history (in Windows 7 the history .xml files are in C:\Users\csny490\AppData\Roaming\ESRI\Desktop10.0\ArcToolbox\History)
3. Turn off/suspend/alter your virus scan software.
4. Delete your normal.mxt template file (make a backup first!!!). This file will autocreate anew when you fire up ArcMap again, but all your settings (toolbars, customizations, etc.) will be removed. In windows 7, C:\Users\csny490\AppData\Roaming\ESRI\Desktop10.0\ArcMap\Templates\Normal.mxt