tgray,
Can you see if your corporate firewall is blocking access to
www.blackberry.net
That was the issue with mine, i noticed in the MDAT logfiles that it was always trying to reach
www.blackberry.net to load xml profiles for the blackberry units, like the 8700 units.
This fixed my issue. I hope it helps you out.
url that mds is trying to reach for 8700 units
EVENT = Unable to load external DTD, schema, or entity source [null,http://www.blackberry.net/go/mobile/profiles/uaprof/8700/4.1.0.rdf]>