OK. I took 80 mp3s burned with MJ. Here's the data for all the CDs:
MPEG-1 Layer 3
320 Kbit CBR
44.1 Khz Stereo
ID3v1 Tag: Yes
ID3v2 Tag: Yes
Copyrighted: No
Original: Yes
Protected by CRC: No
I did a mass tag change, by changing the genre from rock to alternative and then I hit "save." MJ made the change just fine. I checked the tags in Tag&Rename, and both the ID3.1 and ID3.2 tags were changed. I then switched the the taks back to rock in MJ and everything went fine, and was verified by the other program.
Next, I selected a group of 25 mp3s that were downloaded from Napsteresque sites (shut up. They are the only ones I have, the band's music is long OOP, and even unavailble used via eBay/Gemm/etc). These files range from 128-192 kbs CBR, all have both v1 and v2 tags (edited by MJ and/or Tag&Rename)and based upon the info in the comments field, were ripped by a variety of programs, including Real Jukebox and a couple of different vinyl-ripping programs. The result was identical to the results above--not a single problem.
Lastly, I remembered that I was having the problem that you're seeking to correct--namely, that MJ would crash during mass editing (this was just 3-4 days ago, with version 8.0.227). At the time I had downloaded about 500 mp3s from those unsavory sites, many of which were in VBR. I had tried to get them a little organized, so tried to edit the artist tags, for example, but MJ kept crashing (and I've since deleted all those files--either I liked 'em and ordered the CDs, or didn't and deleted them). I'll rip some VBR files in MJ and test, and download some VBR files as well to test.
Oh, in other words--I don't have anything useful to report yet.
Media Jukebox PLUS 8.0.227
CPU: Intel Pentium 4 1793 MHz MMX
Memory: Total - 523 MB, Free - 350 MB
OS: Microsoft Windows XP 5.1 (Build 2600)
Internet Explorer: 6.0.2600.0000
ComCtl32.dll: 6.00.2600.0000
Shlwapi.dll: 6.00.2600.0000
Shell32.dll: 6.00.2600.0000
wnaspi32.dll: 4.70 , ASPI for Win32 DLL, Copyright © 1989-2001 Adaptec, Inc.
Aspi32.sys: 4.7