Had the same mouse wheel issue before. It is very picky as to where your cursor is when you're scrolling with the mouse wheel. Access will also create a new (next) record if you scroll too far etc.
I'd recommend adding a couple of command buttons to your form and having be Next Record, Previous Record, and even a Find Record (uses the Find/Replace text search engine). Those might give an alternative to mouse scrolling.
If the mouse scroll isn't it, can you give a little more info on what isnot showing up for you?
Good luck!