Here are some other suggestions gleaned from other resolutions for Application Errors when starting ArcGIS Desktop. Change the version "10.1" to the applicable 10.x for your product.
Several steps, with increasing levels of intensity.
Delete your C:\Users\<username>\AppData\Roaming\ESRI\Desktop10.1\ArcCatalog or ArcMap folder and try again.
If no joy there. Delete your entire %APPDATA%\ESRI folder.
If still no joy, delete the %APPDATA%\ESRI folder again. And open the Windows Registry with regedit.exe, navigate down to the HKEY_CURRENT_USER\Software\ESRI\Desktop10.0\ArcCatalog key and delete it.
And if still no joy.. delete your %APPDATA%\ESRI folder again. Then back into Windows Registry with regedit.exe, navigate down to the HKEY_CURRENT_USER\Software\ESRI key and delete it.
All will be rebuilt with defaults.