This is a shot in the dark, but try reinstalling MS Access. I recently had a problem with being unable to see the data in Data View as well. Also, I couldn't close Monarch, instead an error message kept popping up whenever I tried. I found a posting that suggested reinstalling Access, and after I did, Monarch behaved normally again. The error message was different than yours though, so it may not work.
Did reinstalling the Access engine (or localdb depending on your Monarch version) fix the issue?
It could also be the CKJ characters causing an issue. If you are still having problems, please can you tell me what version of Monarch you are using an dif it will be possible to get a sample report?