There are a few fixes to this (depending on the underlying cause):
If you're running a custom ROM or a custom kernel, flash back to stock.
Call customer support and:
a) Make sure your ESN and SIM numbers match the ones they have.
b) Make sure there's no data outage in your area. (If there is, 67 means that you can't get a data connection because there's none to get.)
Update the phone's PRL.