XPutImage stops returning to caller

[Phil Hart]

My application calls XPutImage. The target window displays as expected. 
However, after some thousands of successful calls, the next call to 
XPutImage does not return. A stack trace mentions a mutex.

The calling parameters do not change, nor indeed the pixels being passed 
in. The number of calls seems fairly stable on any given computer, but 
changes with between computers.

Any ideas what might be happening? (For what it is worth, the 
application worked flawlessly for millions of calls using a 32-bit 
version of Ubuntu.)

Any help with getting my application to link to libX11-6-dbg would also 
be appreciated. (OS: Ubuntu 10.04.3, IDE: Code::Blocks 8.04)

Phil