SIGILL signal


I programmed an application, which saves the files on the remote computer
using ftp protocol. The application is running without any problem, but now
I test an updated version and it receives from time to time the SIGILL
signal - illegal hardware instruction.
I inspected the code - nothing suspicious.

I am using QNX 4.25, tcpip 4.25, Watcom 10.6.

Does somebody know, what is the problem ?