I've migrated from CCM 4.0(2) to CCM 6.1(1a) successfully, but I've checked that when I list phones (Device > Phone), always the second listed phone appears unknown in status and IP Address, but if you click that phone you can check that is correctly registered and his information from that fields is on third line.
That error appears from that line to the last one, in other words, only the first listed phone is ok, and then the information from fields status and ip address of the 2nd phone is on 3rd phone, the info of the 3rd is on the 4th, and so goes on.
I've tried with a restart, but problem persist.
On release notes of 6.1(1a), appears a bug on CCM UI related but it's not the same, CSCsm09672 (Phone Devices List page can not sort). On that bug, the solution is an upgrade, but the problem is not the same.
Should I upgrade to 6.1(1b) or 6.1(2)?
I think you are hitting this bug;
CSCsl70392 Bug Details
Status & IP not properly associated on Find & List Phone Page
Under Device > Phone the Status and IP address are not properly associated with the correct devices in the list when multiple devices are listed.
CUCM prior to 220.127.116.114 performing a phone search that returns multiple results.
View the device status on the Phone page, or narrow the search so only a single phone is displayed
3 - moderate
In Last 2 weeks
Cisco Unified Communications Manager (CallManager)
The best bet here would be upgrading to 6.1(2). There are many good bug fixes in this release.
Hope this helps!