You ever find out what was causing this? I have the same thing occurring on a client's terminal with Oracle 11g local and server and just upgraded to P6 SP4. Thanks.
P6 supports only 32-bit versions of database clients on 64-bit operating systems
Though your system is 64bit you need to use 32 bit Oracle Client.
64 bit oracle client is not tested.
You are facing this issue only due to this.