Over the past week we've been getting a lot of reports of OWA showing a 'Service Unavailable' error. This seems to be an intermittent problem, as users always get the logon page, but then after they logon, they sometimes get 'Service Unavailable' in the left hand folder list, but still get the message preview pane on the right, sometimes get the folder list OK, but the message preview shows 'Service Unavailable', or sometimes both left & right panes are affected. Apparently doing a refresh once or twice solves the problem.
I've not experienced the problem myself, even though I've tested from home several times. I've had users login and get the error, while I've been watching the ISA logging, but nothing shows up as failed, or denied.
We also run Communicator Web Access, a CRM, and a Wiki thru ISA, all 3 of these seem unaffected, so I'm not sure if this is an ISA > Internet problem, or ISA > Exchange server problem.
The only thing thats changed in the past week, is we've gone from a DSL line, to leased line for VPN/Internet. The default gateway is pointing to the leased line, but all 4 web sites are still published on IP addresses on the DSL line (we only get 1 IP with the leased line). I'm not sure if this is related, or just a coincidence, as the other 3 sites are unaffected!