Weird symptoms what is going on

[dmsee]

For the past week I have noticed that I would get all the bars out. It happened twice today. I will still have signal: saying E and AT&T but there will be no bars
Restart everything works perfect
Cant make phone calls or receive calls when it happens
Whats up?
4Gb iphone 1.1.4

 

[Niiro13]

Have you tried resetting all network settings?

Or if it comes to it: restoring?