I also have this 'No Service' issues after upgrading to iOs5. My place No Service sometimes kena, but with iOs5 cannot recover from it. Now I need to do the flight mode thing if it happens. Sometimes OK, sometimes not.

I will try your method.

Thanks

My workplace got restricted areas that are designed to block phone signals, so 'No service' is normal for me...but what is not normal is  ios5 doesn't search back for the telco signals after the 'No service'.
Yes...so far tried this morning...its OK...I mean 'No service' still happens, but can recorver from it...no need to go through the flimsy process of toggle around with stuff. 

I wonder why need to set it to 'Manual' at achieve this.

I'm also having the same issue.

iPhone 4 on iOS 5.0, Maxis set, non-jailbreak.
Starting 2 days ago, the signal became weird. My house area signal is quite bad, but the problem is once the signal lost, it will never be able to connect back (forever Searching... or No Service). The only solution is restart the device.

I just restored my iPhone. The problem seems gone for now. Hope it won't come back again

It is not a bug.. U tried turn OFF 3G.. This is know issue for Maxis.. If u turn ON 3G and your area the 3G coverage is low.. It will affect your signal to no service.. Turn OFF 3G u will gain FULL BAR..