I had a similar, but horrific experience. I hit the usual ctrl-J from MJ, to upgrade. MJ did the Right Thing and downloaded the update, and started the install, but about half-way through, the machine bluescreened (XP-style, with a memory dump). As a result, my ATAPI.SYS driver was hashed, and my machine refused to boot 2 out of 3 attempts. Usually a powercycle was required. After several attempts in Safe Mode to repair the ATAPI.SYS file, which I assumed MJ installs or updates, but may be perhaps wrong, subsequent launches of MJ caused the same BSOD. However, when I rebooted the next time, I lost two of my Hardware devices - Ethernet (gak!) and my GeForce 256 video card.
To make a long story even longer, I was forced to re-install XP, having exhausted my diagnostic and repair options. Previously, I had never had any issues with any previous beta builds.
I'm certain that this was anomalous, and specific to how weirdly configured my machine is, but it was severe enough that I feel compelled to at least report it.
The bad news: I didn't think at the time to save you any memory dumps, so I'm sorry for that. But, here's my current info:
Media Jukebox PLUS 8.0.282
Install Path: C:\Program Files\J River\Media Jukebox\
CPU: Intel Pentium III 735 MHz MMX
Memory: Total - 785 MB, Free - 337 MB
OS: Microsoft Windows XP Workstation 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: 1.23 , ASPI32 for Windows NT, Copyright (C) 1998 Advansy, TCD Labs, Inc.
Aspi32.sys: N/A