I'm posting this in case someone else has a similar problem:
I had an issue where clicking System -> Package Management resulted in a blank area where the Package Manager should be displayed. Nothing in my error logs, tried all the usual remedies. I set debug on and walked through a bunch of SQL queries but saw nothing amiss. I finally saw a post about turning off js and css compression to solve a similar problem (
http://forums.modx.com/thread/73462/2-2-0-install-issue---blank-manager#dis-post-416581). I set both "Use Compressed CSS" and "Use Compressed Javascript" to No, cleared the cache and was able to load the Package Manager. As to why the compressed CSS and/or JS was causing problems: I'll worry about that some other time.
Time for another cup of coffee,,,
