I had the same problem connecting to the UMA. What is surprising is, I was able to connect to UMA through the WIFI router and then one fine day I replaced the router with the same exact model and configuration (that is what I thought). I have put the solution summary in the end if you do not want to waste time reading my investigation steps.
What was the problem:
UMA worked before on my WIFi and when I replaced it with another router with very similar configuration, the blackberry(s) failed.
My investigation and the Result:
Any WIFI has a feature in which you can choose the type of signal, it can be MIXED, G or B.
The first router, on which my Blackberry phones (15 phones) worked on the UMA had a signal type “B” selected. When I replaced it with a new router, I had configured the signal type to be “Mixed”. Though it connected to the WIFI and enabled web browsing on the BB phones, but the UMA failed.
So, when I got to a point of frustration and was randomly changing router settings in an effort to make the UMA work at any cost, I stumbled upon this. I have experimented enough to prove that this is the reason why my BB phones did not work (note they are all of different model BB phones). When I turn it to MIXED, the UMA on the BBs fail, and when I switch it back to B or G it works. I have put all my routers to signal type “B” and its been working for everybody like a charm.
Summary of the solution
For the UMA to work, the main requirement is that the WIFI router is configured for a single type (G or B) and most preferably on “B”. Do Not at any circumstances use the MIXED.
What a relief. I wish the T-mobile CS knew this or it could be in the min requirements of the UMA access instructions on theirs or BB website
Please tell me if this solution helped your situation.