I have that problem a few times in the past two weeks. I thought it was juice defender doing it but its not. Maybe VZW is doing something to the network. BTW I'm running the stock ROM but making the jump to BB soon.
^Network here has been VERY unstable and inconsistent lately... been on VZW in this area for 2years (since we moved here) and have NEVER had these problems... sadly it's going to be the norm here shortly, especially after the iPhoney releases...
I am having this same problem with no 3g signal once I leave my wireless signal at home. I have noticed this as a once in a while ( every other month) problem for the 12 months I've owned this Droid - but it is now escalated since last week to every day. Grrrrrrrr. I, too thought it was Juice but trial and error told me it was not. OK, so I'm trying the 'fix permissions' with ROM manager and will report back if it solves the problem. I had 156 changes there. ( rooted 2.1.1 phone)
well, I am happy to report that 'fix permissions' solved my 3g signal issues and now my Droid happily alternates from wifi to 3g as before. Thanks for the heads up!!!