I'm having the same problem, using V8.0.318 on Windows ME.
Whenever I make changes to multiple files in file properties (anything from changing genre to adding cover art) and press save, the dialog box says it has saved track 1 -- and then closes. The first few times I assumed it was done and tried to close properties, and MJ crashed.
Because I'm saving to an external drive, I finally noticed that the busy light was still flickering; if I wait, the properties box eventually closes on its own without a crash, but there is no progress bar or dialog box to monitor the process.
Media Jukebox PLUS 8.0.318
Install Path: C:\Program Files\J River\Media Jukebox\
CPU: Intel Pentium 4 1495 MHz MMX
Memory: Total - 261 MB, Free - 80 MB
Resource Info: System - 26 %, GDI - 43 %, User - 26 %
OS: Microsoft Windows Me
Internet Explorer: 5.50.4807.2300
ComCtl32.dll: 5.50.4807.2300
Shlwapi.dll: 5.50.4807.2300
Shell32.dll: 5.50.4134.100
wnaspi32.dll: 4.71 (0001) , ASPI for Win32 (95/NT) DLL, Copyright © 1989-2002 Adaptec, Inc.
Aspi32.sys: N/A