Is it the front or back that is frozen? are you still running the drums in back? In the past, I had a truck with drums that would sometimes freeze the mechanical parts in the drum do to water being present. sometimes the e-brake mech would also freeze causing the drums to stay engaged. I don't recall doing anything except running with the brake on for a little bit to heat it up and then letting it sit for awhile. sorry couldn't be more help.

'88 Raider. 2.6L dead...2.4L swap in progress, AT, 33's, 2 bouncy seat,AC, CC, 2.25 exh, 2" Tbar, 2" BL, rear DB, rear LSD,4.90's, SW hubs,gen2 uca's, KYB shocks, snorkel, elec fan, MSD.

'99 chev k3500 crewcab
'15 Subaru XV
'03 BMW i325