Wifi /UMA when Roaming

Need some help with this one. I have a new 8900 which works well with my home wifi and Rogers. I move down south for 2 weeks and whilst the Wifi says it connects successfully, the wifi symbol is dimmed on the home screen and no data comes across wifi. Under the Wifi diagnostics, it appears to have connected ok, but under the UMA it says "UMA wifi available" but Connection, registration, and authentication not available. Similarly, under blackberry infrastructure there is a big red cross next to connecting.
So I am a bit lost being a newbie to this blackberry thing. Could someone suggest a solution or is this Rogers blocking something beyond my control? The wifi works well over my ipod. Under UMA in the diagnostics it says "Status: ISP error. DNS server cannot be reached" It seems to be a parallel problem to other people have had on the Bold
Thanks