I posted this at graffe's already, but thought I would add it here in case we have any Canadians on Rogers wireless with HTC Dreams.
Rogers decided they'd fix the E911 bug (null pointer exception when a 911 call is placed while gps is enabled) at the end of january instead of back in september when it was discovered. To 'encourage' people to run their update, they've disabled data on any HTC dream or magic that doesn't have this update installed.
The problem with the update is it uses a more recent version of the SPL, fixing the bug that allowed you to get root access to your phone. Also, Rogers is dropping support for the Dream in the near future and won't be providing any new software updates. There is some speculation that they chose to upgrade the SPL to lock out custom ROMs and thus push people to buy a newer phone. There may be some solutions to root the new update now, but you can avoid the whole mess by upgrading the radio on your own.
I followed a combination of the guides at
http://wiki.cyanogenmod.com/index.ph...to_CyanogenMod and
http://wiki.cyanogenmod.com/index.ph...rs_Dream_Radio (I had already rooted my phone, but was running a custom ROM based off the stock Rogers one).
I performed the radio upgrade yesterday around 3:30pm, when I got up this morning at 7:30 my data was back.
Another option is to call up their tech support and ask for a 'network refresh'. I haven't tried this, lots of people have and said it works, but Rogers seems to be getting wise to the plan and is telling their tech support not to do them anymore.
What does rooting your phone get you? Wifi/bluetooth/usb tethering, ability to save your applications to your sd card instead of the internal flash memory, ability to install applications directly from the sd card, access to the paid marketplace in Canada (I'm told, we can't get paid apps by default in Canada), and much much more. Just search the marketplace for 'root' and you'll see all the apps that require root access.