I display several QImages in several modeless QDialogs, each with a Save button. In the save routine I invoke
QFileDialog::getSaveFileName(...)
which crashes with

Program received signal SIGSEGV, Segmentation fault.
0x00002afd7a378adc in QMutex::lock (this=0x61e030) at thread/qmutex.cpp:152
152 thread/qmutex.cpp: No such file or directory.
in thread/qmutex.cpp

I am unaware that I am using threads or am I?
What do I do wrong?
Appreciate any help.

Enno