My friend never had a sim for her iPhone 4. She uses the phone as a skype device and camera (and she loved it that way!). I recently persuaded her to update to iOS 5.1, created a new iCloud account (she never had one), enabled iMessage. However, she does not receive any iMessages. She can send out iMessages but they do not reach me (I have a working iPhone with iCloud, iMessages). I have restarted her machine several times and did a clean install of iOS 5.1. Can anyone tell me what might be incorrect here? (I see that a lot of people have an iPhone without sim working as an iMessage device.)
I can iMessage from my Wifi only iPad, so it can be done. I have a feeling it has something to do with the sending or receiving address. I would check the Messages setting to make sure it is set to her Apple ID/email address. I would also try, instead of her sending it to your phone number, having her send it to your Apple ID/email address, as that is more universally recognized. It would be interesting to know if she can iMessage other iPhones as well.
I turned off iMessage, restarted the iPhone and turned iMessage back on and it suddenly can recieve and send iMessages.