Stranger Error

[avis_phoenix]

In my program draw a path and this path is changing continuously(in a thread), but suddenly appear this error in GDB:

Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0xb5fffb90 (LWP 8229)]
0xb78b60f1 in QRegionPrivate::append (this=0xb6002e48, r=0xb60086f8)
at ../../include/QtCore/../../src/corelib/tools/qrect.h:245
245 { return y1; }
Current language: auto; currently c++

What could be?