Here are two other threads about this issue, a couple of fixes are suggested. I travelled over the weekend and as sooon as my phone went to "extended network" I started getting this error and my phone was unusable. I'm on mightyrom. Definitely a verizon issue with custom roms and roaming. I saw a post that the erice rom doesn't have this issue but i didn't try it.
http://forum.ppcgeeks.com/showthread.php?t=94581
http://forum.ppcgeeks.com/showthread.php?t=97845