Neets:Damager:Forgotten: Yea it's an XT version, did notice in SGS tools when I had a look at the bands WCDMA850 was disabled to start with, though I've enabled it now so it should be working - and it's not.
The default I9000 baseband is 900/2100. I know Doc's kernel is i9000 and his built in modems are usually 900/2100 to match the hardware. Does his Roms include the modem as well?
You could try the JK3 or JK4 or JL3 modems which are WCDMA850 default. Us Captivate users are able to use these 850 modems via an I9000 kernel.
Im sure this is the reason you dont have connectivity. All custom ROMs can allow WCDMA850 to be "selected" however if the model/kernel doesnt match the hardware, it wont work regardless.
As always, flash at your own risk :-)
Edit: Thanks Neets, you got in before me, Yeps try JK3. JK4 and JL3 are also available for default 850 3G/WCDMA
As I recall, Doc started a thread for Captivate users. XDA search is unavailable (to me at least) for 10 minutes. But you could look for all posts by Doc and hopefully you'll spot the Captivate one.
I say Captivate becuase it seemed to be for Bell/Canadian users who have the same (or some of) bands as XT
Yeps Neets, it is the Bell and Rogers I9000s that have default 850 3G bands.. The reason we have had to grab these modems is because AT&T capped the upload speed of the default modem to 300kb/s This was so the iPhone 4 users could get more of the bandwidth, as they were determined to be "more valuable".. pfft.