You might not believe this and I had a hard time with it myself, but Google Voice for the iPhone causes my phone to lose its signal. I could not figure out why my signal would completely drop on my iPhone when it had not been acting that way before. I would lose the signal completely for hours as the iPhone would read "searching." Even worse was when my phone said I had a signal but I was not able to make calls. My SMS messages were delayed by hours and even days, because my phone was acting so strage. After repeatedly rebooting my iPhone 4 I finally realized that the only thing that had changed on my phone in the last week was the installation of Google Voice.

I was skeptical that GV could be responsible as I assumed Google would have tested the app extensively. I kept logging in and logging out of the Google Voice app in hopes that I was simply imagining the relationship of Google Voice to my iPhone's problems. Finally, after not being able to make an important call despite having a signal, I completely removed Google Voice from my iPhone. My signal came back immediately, and I could make calls. I didn't even have to reboot to get the functionality back on my phone.

I watched the iPhone for several days and I never lost signal. In order to make sure that Google Voice was indeed the culprit I performed one final test. I re-installed Google Voice and I immediately lost my signal again. Worse yet, the GV icon disappeared after being installed and only came back after I rebooted the phone yet again. Finally, I completely removed Google Voice from my phone and I haven't had an issue since.

I am able to reproduce the issue at will by simply reinstalling Google Voice. I've done it several times and as soon as it is installed, I start losing my signal.

This is a weird one. I've Googled the issue and haven't found anyone with the same problem. If you have the same issue, please let me know in the comments.

Waiting for an update of Google Voice that actually works on the iPhone...