I'm currently using Win2k's built-in ICS and it works fine except for one thing : it sometimes dials for no apparent reason. I suspect this is because I put on dial on demand.

Is there some sort of software, console, whatever I could put on clients to let them dial/hang up manually ?

I tried Sygate, I know it puts a console on clients that does exactly what I want but it has a bug. It sometimes (often) doesn't hang up the modem correctly, I can't dial-up anymore, the modem is jammed. The only remedy is a reboot.