I made some tests, and it seems, that it's the combination of the M4Board-based Network Daemon and the 3D Starfield Screen Saver.
It is crashing after a while after the screen saver has been started. This also happens within a Telnet session, so it's not syMIRC related.
The screen saver is using screen MODE 0, and the M4Board requires upper rom access (rom and screen mode switching use the same register), so maybe there is still a conflict sometimes, I will check this...