Wow, geeee, that was close!
Today my whole IBM Notes 9 environment crashed so badly after saving a LotusScript source that was full of errors, circular uses and other mess. I have to say that I turned off "saving LotusScript with errors" in the preferences. That maybe caused the whole mess.
Resulting in a client that refused to start again, after renaming the workspace folder, let notes create a new one and copying the applications folder content into the new one I almost gave up. I was facing to a completely messed up Notes on my machine - and this while I was with the customer. What a pitty.
After trying to re-open the database with a 8.5 client (the same result as with 9) I remembered the fact that I carry a VM with me with Notes 7 installed. So I setup this one to open the database from my local server, opened the database with the good old Designer 7, removed all errors in the scripts and recompiled the whole database. Everything worked fine. Designer 7 is a genuine C++ application that does not suffer from the Java backbone that killed my Designer 9 everytime I openened the database in my workspace. There must be something the developers missed here, because this situation results in an infinite loop. Done with Designer 7 I just gave my 9 a try - and: lucky me, everything worked fine again. I finally cleaned the whole project to be sure not to miss something - "clean" sounds fine for me
So you ought to carry a VM with you with Designer 7 inside to fix a mess like this!