When this happened to me, it turned out the drive was full.

On the system I use at work, the I: drive is a "virtual" network drive where I'm supposed to store my private files, where they will not be viewable by any other employee. It has a size limit that makes it much smaller than a typical physical drive.

I discovered that RealPlayer was set up to store its temporary files on the I: drive. I changed it to store them on the C: drive, and there was no further problem.

I use RealPlayer to listen to online streaming audio from a radio station, which RealPlayer downloads to a temporary file. These files can be quite big if the program is several hours long.

If you don't really have an I: drive, or if the I: drive is meant to be some device that is currently disconnected, and some program thinks it needs to save data to the I: drive, then that could cause the problem, I suppose.

I'd say, check whatever programs were running at the time the error occurred, and find out where each program stores its data.

For example, in RealPlayer, click "Tools" then "Preferences" then "General" and you will see where it saves its files. Click "Browse" if you want to change it.