RRAS modem conundrums

Recently configured a RRAS server on Win2k

Dial in working perfectly for 3 days until somebody complained this morning re errors.

The configuration was examined and NOW the modems no longer negotiate incoming connections. The modems just makereally stupid screeching after an initial 5 second normal negotiation. Doesnt matter if we use win98 win xp clients with diffferent modems etc.

I can dial out with hyperterminal from the win2k server. It seems that the RRAS settings are preserved in the registry so removing and readding doesnt help. Tried a known good external modem on this server and it does the same thing.

Can someone recommend a Win2k RRAS troubleshooting process?