... and almost immediately crash. First, I get a popup with the remarkably useless error message "Attempted to perform an unauthorized operation". Then clicking OK gives me a different error popup saying "An unexpected error occurred in the Configuration Framework (in Main). See below for a detailed explanation" with the so-called detailed explanation consisting of the one line "Object reference not set to a instance of an object. (Configuration)". Clicking OK on that dialog brings up the infamous "your application died, would you like to send debugging information to Microsoft?" dialog.
Not what I needed.
I tried all the obvious steps - uninstalling and reinstalling, talking to the other folks in the company who use BizTalk (all two of them), searching the Web and the Microsoft site in particular for similar situations - and came up with an awful lot of nothing. Finally, I called in the big guns; last Wednesday, I opened up a Microsoft support ticket. A few hours later, I was on the phone with a BizTalk support engineer, walking him through the problem. When he saw the failure for himself, his immediate response was "Wow. I've never seen that before." I took that to be good news and bad news; the good news being that at least I'm not crazy and the bad news being that this isn't going to be a simple fix.
And it wasn't. Rather than bore everyone with a blow-by-blow description of all the debugging steps, I'll skip to the good news. Late this afternoon, we tried another iteration of installing from scratch, with the BizTalk guy watching over my shoulder  - and this time, the configuration manager ran perfectly.
So, after nearly a month, I once again have a working copy of BizTalk on my workstation.
Whew. Now I can get my frustrations the normal way - by having the business decide to change the requirements on me, well past the last minute.
 Actually, it took a few iterations before I got a new workstation that I could actually install stuff on. But that's a different rant entirely.
 So to speak. We were using Microsoft's Easy Assist to share my desktop with him, and it worked pretty well.