I am chatting with TMO right now and they are as perplexed as me.

i would call them and ask them to reset your internet connection on your account

I did that. At first, they tried to push me into the smartphone plan, but after I explained everything was working fine with the 5800 before today they tried to work through it. They have absolutely no idea why it isn't working. I'm about to pull my hair out. Using internet data OTA 3g is one of the main reasons I got this phone.

i guess the only other thing you can do is reset the phone to factory state

Ok this is my first post and I see tons of ppl getting flamed for being dumb on here. Got my N900 yesterday. I have the Even more Plus plan (with 1000 minutes as if that mattered) for 69.99. I hook the phone up, voice and texts works fine but for data... I get the Tmobile symbol with a little 3G next to it but when I go to click on it, it says "internet connection failed" almost immediately. I came on here and saw the other APNs people are using. (the phone was preset to internet2)

I inputted epc.tmobile.com and connect and it SAYS I'm connected at 3G and 3.5 and does NOT tell me the connection failed (I even get the proper connection icon next to the Tmobile service symbol, but no pages are loading.

So I tried the wap.voicestream.com, connect the phone (everything appears to be good) and then open a webpage and I get this message on a web2go webpage "Subscription Upgrade Required.. Your current plan is not compatible with this device. Please click here to view your plan options."

Do I need to call these peckerheads or am I doing something wrong? Because as far as I understand I believe my Even More Plus plan should work... grrrr

Oh and it may be of value to note that yesterday before I fired up the N900 my SIM was in a tmobile/htc shadow and the internets worked just fine on that.

did you get the error for internet2?
which internet plan you have? epc works for tzones , internet2 (at least for me) only works for unlimited web for dumbphones

Yes I got the error "internet connection failed" on internet 2. epc appears by all measures to connect but then won't actually take me to a web page, and wap tells me I need an upgraded plan. My internet plan, for now, is bundled with the Even More Plus 1000 minutes unlimited text unlimited web plan. As I edited my note a minute ago, the internet worked on the Tmo Shadow I was using yesterday. Maybe I should ditch the Even More Plus and sign up for the regular Even More plan with dumbphone?

i heard some ppl have problem when they switched from shadow
my suggestion go to your account change a phone to like a samsung 879 i think the brown one and choose unlimited web for dumbphones for 10$ and use settings for internet2.voicestream.com
and make sure u change settings in a browser for cache size from 5mb to 40mb

My problem was finally resolved when I left my house. When I got outside of my wireless home network it was fixed. Which tells me it was one of two things:

1) My phone literally had to get away from my home network to work
2) Sometimes it takes several hours for TMO SIM to recognize and calibrate with the new phone.

I am using internet2.voicestream.com for what it is worth. Also, I am able to connect to TMO internet without a problem from my house now.

I have the old T-Zones $5.99 plan. I can't remember what the plan provided.
I don't want to get a big bill by downloading too much. I think it was unlimited web and email through a proxy. Does anyone remember? I couldn't find it on the T-Mobile web site any more.

Thanks