I had installed v11 on top of v9, which I guess is what caused the problems.
There's a window that pops up when you install v11, that says more than one version can co-exist on a computer. I think that message should be changed to say that only v10 can co-exist with v11 on the same computer.
I did as Alex suggested, sort of:
-backed up the library and .jmd files to a different directory
-uninstalled MC11
-deleted all J River folders in "C" drive directory and C:\program files, (I did not clean the registry or Documents & Settings).
-re-installed MC 9
-uninstalled MC 9
-installed MC 11
and voila, MC 11 works like a charm!(and I have to say, I'm impressed!). The other problems i mentioned in another post have also been resolved.
I didn't do the in-depth cleaning as I didn't want to have to restore MC 9 (I had just lost my internet connection, which was only restored an hour ago).
Excuse me, now, while I go play with this new library browser thing (pretty cool stuff).