Google Voice incompatible with your iPhone 4?

Google Voice became available Tuesday to all U.S. residents, but it seems not everyone will be able to use it on the iPhone 4.

The Google Voice service offers a number of features, one of which is forwarding calls made to a central number to multiple mobile phones and landlines.

The call forwarding feature, which calls your preselected phones when someone dials your Google Voice number, is functioning spottily on my iPhone 4, in any event. Set-up worked just fine--I was able to call my iPhone 4 number and activate the phone, but on a couple occasions, ringing Google Voice caused every phone I had to trill except the iPhone 4. The times calls to my Google Voice number didn't go through, I was able to receive text messages and view missed calls.

I'm not the only one. One CNET reader e-mailed a detailed account of how he tried to fix the problem on his own, after activating the iPhone 4:

"When I activated the new [iPhone 4,] it took me back to AT&T's voice mail. I tried setting it up again in Google without success. The problem is that to use Google Voice voice mail, you need to do a "conditional forward," which for at&t the code is *004*1[number to forward to]#. When I enter this code on the iPhone 4, it gives me a bunch of errors and nothing happens...I also read somewhere that I needed to use two "**" instead of one, but that didn't work either."

When calling AT&T's customer support line, our reader said he was told his fix should work.

We're looking deeper into the issue, which could be one more of a number of complaints buyers have had with Apple's iPhone 4 since snapping it off store shelves yesterday, or receiving it on preorder as early as Tuesday.

Google was not immediately available for comment, and we're in the process of reaching out to AT&T and Apple.

In the meantime, if you're a Google Voice user who also has an iPhone 4, let us know in the poll if you're experiencing problems or, if like the antenna issue, this is a rare incompatibility on certain iPhone 4 handsets.