When you compact/repair and leave the db open, Access makes a temp copy of the db and compacts one** (I forget if it's the copy or the original) which is why you can sometimes run into issues when disk space is getting low. I would not expect this to cause either db to reload since you say you are doing this on close so I'm afraid I wouldn't be much help with that situation. However, I can say that compacting like this is usually a bad idea. First, you should backup before you c/r and I suspect you are not. Also, the back end should not need regular c/r and certainly not after every session. Besides, if each user has their own front end and they connect to the be, I don't see how you can c/r the be anyway - certainly not safely. In addition, the fe should not need c/r nearly as much as the be so doing so at the same frequency is probably severe overkill.
There are several things that are considered contributors to db bloat and some situations definitely experience this, but often it is a misconception on the part of someone that their file size grows too large when in fact, it is nothing to worry about. You should state what file sizes you were experiencing that made you take this approach.
EDIT - ** actually, I meant the copy is made regardless, but I didn't see how doing a c/r and closing the db would raise your password form. If doing a c/r and not closing the db, then I would not be surprised that your password form is raised again.
The more we hear silence, the more we begin to think about our value in this universe.
Paraphrase of Professor Brian Cox.