Weird debugging problem

["Joshua D. Boyd" <jdboyd@sigmaelectronics.com>]

I am working on GNU/Linux 2.6.15 with GNU gdb 6.4-debian and gcc version
4.0.3.  I am trying to debug a threaded program that stops mysteriously
without stating a  particular fault.  My intention is that threads are
created during the programs start-up faze, then the same dozen or so
threads remain there the entire run time.  Prior to every
pthread_create, I print something to identify what thread is being
created at that time.

When I run the program in gdb, eventually (usually after running for 12+
hours), I get the following:
[New Thread -1734661200 (LWP 67296)]
Can't attach LWP 67296: No such process
(gdb) 
Now, if I'm not mistaken, that is not a valid process ID for Linux or
most other Unix type operating systems.

If I do a back trace at that point, it reports the current thread is the
main parent, which is currently in a nanosleep (and that thread's normal
behavior after start-up is to sleep most of the time and do house
keeping tasks when it wakes up).

At this point I am at a complete loss about what could be happening or
what to try next, so after scanning through archives and a short period
of lurking, I decided to hope that someone here could provide some
advice.