The following error occurs when describing a table over DB link:
"ORA- 00942: table or view does not exist"
User account does not have access to sys.DBA_IND_EXPRESSIONS view. This view is used in background queries of Toad.
1. Select View | Toad Options menu option
2. Go under Startup section
3. Uncheck "Access for access to DBA Views" checkbox, hit OK and reopen Toad.