Weapon firing on hud

[664a6f3483f38Al]

Really annoying bug just randomly appeared this morning while playing ss2, when I try to click things in my HUD, be they weapons, the hack button or the PDA button - my weapon fires.  Total waste of ammo...obviously on a game like system shock!  Any ideas on how to fix this please?
Thanks!

[664a6f34840edAl]

Sorry for the reply to my own question - couldn't edit.

I have sorted the problem by deleting my user.bnd file, but any idea on how to stop this happening?  Or is it a regular bug with modern pcs and this amazing game?

[664a6f348434cvoodoo47]

https://www.systemshock.org/index.php?topic=78.0