To answer a few questions:
1-I *WAS* using the 2nd disc of the 5.9SOHO-pack, not the " straight one" from your site.
2-The Hardware: the very same, I run all other versions on: 1667Mhz Athlon, 2Gig DDR, 200Gig WD Caviar, Nvidia Geforce 5600-*somewhat*(256MB) AOPEN DVD-re-writer, LG "lightscribe" DVD-writer, 4Gig Quantum Bigfoot, SoundBlaster Live!, Realtek8139, a multicard-reader/usb-hub of un-remembered origin(but it works...) and a 22" IIyama E2202WS.
5.9std and 5.8SOHO run on it without a hitch(albeit due to my own meddlings, the 5.8SOHO is on its way down the crapper at high speed..), so the hardware shouldn' t be the problem.(but more on that later!)
3-I could still access my root-account just fine, but Amarok just "flashed up" and then dissappeared completely. Not even as a trayed icon. That problem, however was gone after the next reboot(after I posted this). Not a friggin' clue whatsoever. Could' ve bee a fluke, rooted in other issues.
4-The "Opera-reset" happened
in my root-account!, which is what really irks me;
I am the ONLY one to change anything in the root-account, not any ******* piece of bits.
5-"useradd"... Right... And I was scratching my head why "adduser" didn't do anything.... bloody "Emmenthaler" memory of mine...
And now coming back on a *somewhat* hardware related point:
For some odd reason, the BIOS-clock yearcount was suddenly set to 2069.
I'm **** sure , this wasn' t the case two days ago.
I first thought of checking the BIOS again, since I tried to test-install another version on a spare partition and no matter what version I tried(all the way back to VL4.0std..) every install failed at copying one of the big packages(usually kernel-sources or OOffice) and I met this problem a few years back on another machine.
My 5.9SOHO is still b0rked, though. Still crippled after install.
Regarding xmms: Between the tinkering(what a way to spen a rainy sunday...

) I checked their own site and found out, Slackware removed xmms from their packages somewhere last year. Had to do with xmms being too tightly attached to Gtk+1 and giving problems with Gtk+2 or such.
I also found, there's a xmms2, built on Gtk+2. Maybe something to keep in mind? Linky:
http://wiki.xmms2.xmms.se/wiki/Main_PageBtw.-couldn' t get Audacious to play my files either...
Ergo Conclusio:
The very 5.9SOHO disc, I rcieved appears to be a "bad burn" (also had problems with it on my (NEW)laptop.) and there's something in the MMBD coming with it, that sends the already shaky installation over the edge in several fields. I have no clue as to what it is exactly,though.
Maybe some system calls are made during the install-process, that would go unnoticed and without harm on a healthy install, but can send a wonky install bonkers.
While the install of 5.9SOHO wasn' t really "splendid", the real problems(Opera-reset, inaccessible user-account, inabillty to re-create account) all started
after the installation of the MMBD.