I currently have a non-threaded application, which has library calls that are called back from a single threaded caller library. Once a call is made, the caller thread is blocked from calling another library function. The caller library is a binary that is linked into the final executable. When this happens my memory buffers are randomly being overwritten with other data, causing my application to crash. I can put a write statement at the top of my callback library routine and it will randomly have a parameter value in it instead of the write string. This only occurs on PGF77 and does not happen on INTEL or on TRu64 5.1A or B. Can anyone shed any light on this issue ? I’m using PGF77 5.2-4 on a RHEL 4 update 2 platform.