I have SPS525G2 phone with fw 7.4.9c, connected to SIP provider and have the same problem, like described in
https://supportforums.cisco.com/message/3171421#3171421 with little difference:
Phone does not search and display incoming caller name by phone number in local personal address book, but if i set personal ringtone for this contact, phone plays it.
After call, when I look in the history on the phone, I see caller name and phone number.
When I look in the history on phones web page, I see NULL in Caller ID column.
My sip settings: