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Here is a new great error for MSCRM 4.0 "Request IP Address has different address family from network address.". You may get this when openning MSCRM. You may also get this in the event log. If you are seeing it in the event log it means that Workflow doesn't work, Imports never happen, emails don't flow and Outlook clients cannot connect. Lastly it is likely you are using Windows 2008 (although I suspect this can hit Win2k3).

Well what is happening is that MSCRM 4.0 doesn't work with IPv6 (as pointed out at, but what is happening is that the names are resolving internally to IPv6 addresses. The easy way to test is ping the server name and localhost for instance, if you get an IPv6 ip address then welcome to the black parade.

The fix for this is simple, open your hosts files (<system drive>:\windows\system32\drivers\etc\hosts) and add a line for your server name there with an IPv4 address. Save and ping again to make sure it is working. Once it is, do an IISReset and it will be working!