You mention they aren't large files, but do they contain a lot of sheets, formulas, macros, etc..? Because this can be what it bogging it down most times..
I have had a similar situation where I could open up a simple, but large 100MB excel file in almost on time. But I have a very complex spreadsheet with a lot of sheet cross-referencing that took about 2-5 minutes to open up.
If it's becoming a big hassle for you I might suggest any of the following:
- Change the workbook calculation to Manual model... and that way it won't try and calculate everything when you open it every time (if you have a lot of them)
- If at all possible remove extraneous information from the workbook to trim it down
- If at all possible try and split the spreadsheet into multiples to try and figure out where the problem lies.
These are just a few suggestion, the first of which I think may help the most.