I've encoutered this problem also today. An application with 8 threads each with its own session faulted everytime I launched it (after a few minutes) with "External exception EBF00BAA", I've tried to obtain a stack trace with little luck. It took time to trace it to the OCI client. Tested with 11.1.0.7 (no patch applied), Windows 7x64 and 2008R2x64. Using 10.2.0.5 it worked. With other three applications which are not multithread there are no issues. I'll try the workaround suggested here:
http://www.allroundautomations.com/threads/ubbthreads.php?ubb=showflat&Number=37307#Post37307, because there is no trace of such a issue on Google, I wonder if this is DOA specific for some reason.
I'm going to test 11.2 tomorrow, and applying the latest patch.