When the very first connection, after starting TOAD, is to an 11g database, if it is closed and a connection to a 10g database is made, that works OK. It is possible to then close it and start an 11g database and that will work. So, connecting to databases in an 11->10->11->10->11->10-> order is always OK. However, if the first connection made is to a 10g database and then to an 11g database, it fails.
The error is: " the procedure entry point upigbp could not be located in the dynamic link library OCI.dll "
WORKAROUND:
None
STATUS:
Waiting for a fix to be released in a future version of Toad for Oracle.
RESOLUTION 2:
If there are multiple Oracle clients, ensure that the latest Oracle client (or the one primarily used by Toad) is listed first in the Windows PATH environment variable.