I am having a bit of a nightmare with a few AutoCAD drawing files. I am running AutoCAD 2004 on our company's windows XP. I was working on one of our layouts (drawing file size about 5MB). Did some mod work to the drawing and then tried to save. After a long time an error message came up saying "AutoCAD Message - Error - writing/closing file". I had to then shut the drawing down but when I tried to open the file again, it comes up with not being able to open the drawing as it contains incorrect or corrupt material. i tried the recover command but no luck. I got the file back from our server, but same thing happened again. Over the next couple of days the same thing happened with another couple of files (both large files). This doesn't seem to happen to every file and prior to this I have had no problems.
I don't know whether this is a problem with either the drawing files, the AutoCAD software or our network. Any ideas would be well received.