Update: I tried to do the above and the same IP managed to get logged in again afterwords. So either GMail's communication with TMobile is less secure than it should be, or the IP in question is not from anyone who should be logged in there, and someone's actually managing to be on my account. (In which case how they managed to get my account password as I changed it from the N900 I could never know. A keylogger on N900 would probably fail. Similarly, I doubt a packet sniffer could figure it out since our WiFi is WPA-key-protected and, as far as I know, uses encryption.)

IP is 24.92.29.209, if anyone knows what that's from. It's neither my N900's nor my home computer's.

- Edit -

Same issue with the account on my gmail account that has never been accessed by mobile phone. (That is, another session is being reported, labeled as "mobile", by GMail, same IP as above.)

So at this point I have no idea what this is about... I'm at my family's home right now. I have no idea how they have their router set up (dad's a programmer, not a newb like me, maybe he has the router mask it's IP and it's keeping the connection live - but this is the first time it's happened).

Honestly, I'm not sure where to go with this from here. Is anyone else who's having their GMail go to mobile-version in MicroB having Gmail tell them they are getting random IP connected to their accounts simultaneously as their own?