A. You can't open .fla files saved as CS5 version files in Flash CS4. So if the file that you are attempting to open was saved from Flash CS5, you can't open it. The file format has been completely changed from version CS4 to CS5.
B. You may need to use the "Open" command from the File menu. If you attempt to open a .fla by double clicking on the file name, it may not open. This usually happens when the file was created on a different platform. If you are attempting to open the file directly from the server, try downloading the file to your desktop first. Then open the file.
C. If the file was uploaded to the server incorrectly, then the file will not open. You have no control over this.
Do others in the class have the same or similar problems with the same files?
Those two errors that you quote, #1053 and #1065, are Actionscript errors in the files themselves. You have no control over this problem.
Thank you so much for your complete answer of my question! I am in the process of getting CS5 so hopefully that will resolve the majority of my issues. I have posted in my online classroom asking if anyone else is having this problem, but no one has indicated so yet. I will also try the Open command instead of double-clicking as I had been doing.
Again, thank you so much for taking the time to post an answer to my question.