Which version of Illustrator 10.0.x are you using? Does the progress bar go away if you leave it? Does the "action" complete? Have you tried removing the preferences files with AI closed, then doing a re-start?
When is the progress bar appearing...when you open the file?
Does your artwork have lots of linked images and/or art styles in the very first layer?
If you've got linked images...try moving them out of that first layer. Easy to do just by creating an empty layer. Then save the file and it should open up again much faster than before.
This File Open performance issue requires BOTH many linked images AND an expensive to calculate art style in the first layer.
First thing is to patch through to AI10.0.3 and see if that fixes things.
Then make sure nothing by Norton is installed and running while you're using Illustrator. If that fixes things, one cause of speed problem with AI9/10 on Windows machines seems to be caused by at least 2 different Delete Protection utilities – like Norton. It seems that AI9/10 continuously replaces the AdobeFnt.lst file(s) in several directories and each time the previous version is deleted. The Delete Protection utility is taking up so much CPU time protecting all these deleted files that it slows down AI9/10 to a snail's pace. When you disable delete protection for *.lst files, all should be well! Check this out: <http://www.adobe.com/support/techdocs/25316.htm>