I have a server on my local network, with my website's folder as a network drive under Windows XP. All loads fine, edits are fine etc. etc... however, (it seems random) I will sometimes get a popup notifying me that the file has been modified, would I like to reload?

I am THE ONLY ONE editing the file.. it seems to have trouble since it isn't on the local drive. What can I do about this?

It may happen that you are NOT the only one who works with the files.
It's possible that you have a software that monitors file system activity and does work not so transparently. For example its known that some antivirus software do their work very actively, modifies access and modification date/time stamps and this alone may cause other software to see these changes and think the files are changed.