OS X 10.8.3, build 168. I'm still experiencing the occasional crash when tagging files -- usually not right away, but after I've done a few. Typically it's preceded by a period (3-5 seconds) of disc thrashing. Mostly ALAC files, but this morning's happened with a FLAC (24-bit, 88.2k resolution).
Updated: it happened again just now. Here's the crash report:
Process: Media Center 18 [40829]
Path: /Applications/Media Center 18.app/Contents/MacOS/Media Center 18
Identifier: com.jriver.MediaCenter18
Version: 18.0.168 ()
Code Type: X86-64 (Native)
Parent Process: launchd [172]
User ID: 501
Date/Time: 2013-04-13 12:10:58.942 -0700
OS Version: Mac OS X 10.8.3 (12D78)
Report Version: 10
Interval Since Last Report: 2164962 sec
Crashes Since Last Report: 12
Per-App Crashes Since Last Report: 2
Anonymous UUID: 3B7B6593-9DF2-49AA-DA16-3BC9566995E1
Crashed Thread: 0 Dispatch queue: com.apple.main-thread
Exception Type: EXC_BAD_ACCESS (SIGSEGV)
Exception Codes: KERN_INVALID_ADDRESS at 0x00000001ffffffff
VM Regions Near 0x1ffffffff:
CG backing stores 00000001c5e76000-00000001c5eb3000 [ 244K] rw-/rw- SM=SHM
-->
STACK GUARD 00007fff5bc00000-00007fff5f400000 [ 56.0M] ---/rwx SM=NUL stack guard for thread 0