I'll try

Once I got fMMS and fAPN installed and setup, I had 2 GPRS connections, the original "T-Mobile Internet" and "Tmo MMS". My N900 was defaulting to "Tmo MMS". I tried re-naming to "zTmo-MMS" no change. Renamed original to "zT-Mobile Internet", no change.

So I fired up fAPN and created a new APN "T-Mobile Internet2" and copied the correct settings to it. Unfortunately, that didn't work either. "Tmo MMS" was still the default APN. So I copied the "Tmo MMS" settings to "T-Mobile Internet2", then copied the "T-Mobile Internet" settings to "Tmo MMS". I just switched the settings.

My N900 still defaulted to "Tmo MMS" but now it connected to the internet properly. So far so good. I then re-named "Tmo MMS" to "T-Mobile Internet1" and re-named "T-Mobile Internet2" to "Tmo MMS".

Now my N900 defaults to "T-Mobile Internet1" (formerly "Tmo MMS") and connects up properly. Fired up fMMS and made sure it was pointing the new "Tmo MMS" (formerly "T-Mobile Internet2"). Presto, everything is working correctly.

*edit* I currently have 3 APN's: "T-Mobile Internet" (original), "T-Mobile Internet2", and "Tmo MMS".

@frals On a side note, when using fAPN to create "T-Mobile Internet2", it creates a gconf key of "T", when then trying to create a new "T-Mobile MMS", it just renamed the earlier created APN. In other words fAPN (or the N900) ignores everthing after the "-" for naming. That was 3 reboots and 6 name changes to figure out.