I have just replaced my Apple Airport Extreme router for a new one with exactly the same configuration, however all of a sudden IWP will only work for one session and then all attempts to access it give a "database unavailable" error.  The only way I can remedy this for the moment is to turn IWP off and then back on again. I have made absolutely no changes to my Server configuration to provoke this and it has been working perfectly since I installed FMSA 12.   Any ideas what may be wrong and what needs to be done?

On your network are you using Cisco based managed switches ? and who is your isp ?

No Cisco based managed switches.  And the isp is a Swiss cable company, Citycable.

I have had a similar problem with managed switches. Had to put router on un managed. other than that I would check the settings again, even check the settings on your cable modem if possible. It also could be coincidence but the network card in the computer can be going bad..  or the new  router is bad.  if you still have the old one and it works ok, try putting that back and seeing if the problem disappears.