Randomly, the session browser layout will change. The first column will expand no other columns are visible. The scroll bar seems to be enabled still but it doesn't move. There is no wa to get to the end.
The list of "visible columns" for the display settings is still correct and resetting the columns doesn't help.
Size setting is unexpectedly changed in settings file.
Exit Toad. Go to your applicate data directory, C:\Document and Setting\<user>\application data\Quest software\Toad for Oracle\<version>\User Files. Find and rename SessionBrowserTree.ini
Waiting for fix in a future version of Toad for Oracle