Drmike... my apologies. I'm new to THIS forum and assumed that Denis would have been a known quantity here because of his Semio Logic theme and likely WP contributions. But I do FEEL your sarcasm (or is it rudeness?), and find it counter-productive.
He did transfer over a setup that worked already, initially. But then tore it all out including the database and started over with a plain mu install. Those indications of plugins (in error log) are PREVIOUS to his removing everything and starting with a plain install.
The mu install just won't complete... well, all the files install but the site then produces a blank page after initializing.
And yes andrea r, I suspect it's a quirk with Plesk for a Special setting needed to work with WPmu - and it's NOT been set properly yet because no one knows it's supposed to be. I'm just trying to drill down to find it.
It's something having to do with the database and Mu speaking to each other (or NOT speaking to each other, more precisely)
I'm at a bit of a handicap as to WHAT's been done so far, as this problem has just landed on my plate this morning. And although I've done zillions of WP installs, I've yet to install WPmu. This will be my first - and on a Plesk server to boot.
I'm trying to get tech support at RackSpace to help from their side and now they've escalated this to a SENIOR support person and I'm waiting.
I JUST thought someone here may have done a successful mu install on a Plesk server and would have a few pointers and things to watch out for. I've found that if I at least know the AREA for tech support to focus on for THEIR server setting and checks, it often really cuts to the chase.
Although this IS the Mu support forum - I AM truly sorry for my Mu noobiness. Thanks very much for the help, people.
Deb