I'm not on tmobile, so I don't know those apps, but maybe this will help.
I have an 8700c (Cingular) and I'm connected to our corporate BES. At the office, if I try to use AIM on my computer, I have to configure it to use port 23 rather than the default port.
I found that when using Ramble
(free Berry AIM client), I had to configure it to use port 23 there too.
Like I said, it may not help, but if you have an option to change the port and you're on a BES, you may want to give it a try.