Onunload/Onload 7.13uc1

I have successfully onuloaded tables having 25 - 30 million records - approx. 5 gig of data, and successfully onloaded the same table back into its original dbspace and database name. However, I am now encountering error on onload of tables that are smaller as well as larger in size. The Error message is not posted to the online.log. I either receive "Error writing Buffer" or "Error Reading Buffer". I have spoken to HP (platform HP-UX 10.01) with regard to this generic error message and I was told in was not an O.S. message. They believe it is related to the Informix Online Engine. I've also tailed the sys.log and there was no message posted. Prior to upgrading from 7.12uc2 this error would bring informix off-line. Any suggestions?