Both messages are referencing the following URL: file:///C:/Users/MYUSERNAME/AppData/Roaming/ESRI/Desktop10.0/ArcToolbox/Dlg/MdDlgContent.htm.
Since this file in in your user profile area, you may want to try regenerating your ArcGIS app profile:
1. Close all ArcGIS apps
2. go to your %APPDATA% folder
3. rename Esri to Esri_ld
4. restart ArcMap
You will lose your set up ArcCatalog Connections, but you'll get a nice new clean user profile.
I followed this advice [reset user profile] as I had a similar error message: [ATTACH=CONFIG]34969[/ATTACH]