What is wrong when an iPhone ends all calls in failure, texts fail yet the data works? I bought a used iPhone 4, originally from the UK (now in Denmark). The phone has been reset/restored, updated to 5.0.1 and appears to be functional with 4-5 bars and the "3G" icon next to them. The phone worked perfectly with the previous owner's SIM card.

However, all outgoing calls fail immediately with a "call ended" message, incoming calls produce a two-tone at the caller's end and texts can not be sent, yet data works over 3G. Strangely, I have made 1 outgoing call while connected to iTunes, but a second attempt failed. I am experiencing this using a known-to-work SIM card from another iPhone.

In Xcode, the console produces these messages when trying to make a call:

kernel[0]: computeProxBaseline.. This is a negative slope unit
kernel[0]: computeProxBaseline.. This is a negative slope unit
kernel[0]: This is a negative Slope unit. Going to use a fixed power of 3. This will behave like an Apex unit


Googling for this only revealed this unhelpful pastie: http://pastebin.com/q8vMQvpv

So, the phone or text is not working but data over 3G is.

Any suggestions?
The phone was replaced free of charge with no clear explanation of what was wrong. The replacement, however, would indicate that it was not a software/firmware issue.