Finally, v8.X is stable.
I had to completely uninstall MJ v8, as per instructions in previous forum mail. I had to use regedit and remove anything with JRiver and MediaJukeBox, as well as uninstall eveything using Add/Remove programs from the Control Panel.
Before uninstalling, I had saved my registration file *.mjr from the website. I rebooted after uninstalling. I went back and downloaded MJ v8 onto my disk, instead of installing from the website, as I had done before. I then installed MJ from the downloaded executable. I double-clicked on my registration file and MJ accepted it.
I rebooted my system again, and have not had any more enc_wma.dll crashes. I have successfully recorded from my sound card's Line-In and created *wma files. I have also encoded and decoded these same files with MJ as a test.
MJ v8 is just too slick for me to completely give up on it. However, I do not think someone like my wife would have had the patience to debug and correct MJ's install issues.