I am having trouble with a machine running Arc GIS 9.3. When one tries to save an mxd, ArcMap stops responding and just hangs. I have even tried with an blank new mxd but the moment one clicks save it hangs without even opening the dialogue box that allows you to navigate to the location to save. Please help
Have you tried to wait for few hours?
I have noticed similar behavior when I had broken links to network location which I used previously from ArcMap (open/save mxd). i.e. when taking laptop to new network environment. In such case you can take your laptop to previous net environment, try to use ArcMap there and open/save data from your local HDD. Or try to wait for quite a long time (few hours).
I hope it helps you!
Try using MXD Doctor - this can fix many issues with 'broken' MXDs. I assume that this particular MXD is now always giving you problems even after a fresh re-start.
Additional tangential info
Another situation (and I don't know how Arc gets itself into this situation but I have seen it many times) is when Arc has not completely shut istelf down properly. It looks like it has but there is still an ESRI process alive behind the scenes. This can also impact your ability to edit files as well as save MXD documents because the locks persist. I can't tell if this is effecting you but it worth a look if/when you get any strange locks or MXD behaviour with Arc.
Press Ctrl+Shit+Esc to open the Windows Task Manager. Since you are trying to save, you should have at least one instance of ArcMap in the applications tab. Right click on it and select 'Go To Process'. Note how your current process is highlighted. Now click on 'Name' to sort the processes alphabetically. If you have another entry for ArcMap, a previous instance of ArcMap has failed to shut down correctly. Right-click on the ArcMap entry which is NOT highlighted (i.e. the one you are NOT trying to save and which ought to be dead anyway). Select 'End Process Tree'. This is different to End Process and it kills all dependent process associated with the un-dead ArcMap instance.
This pre-supposes you had at least one other ArcMap instance open prior to the one you are trying to save. I can't guarantee this is the solution to your problem but it can be a solution to many unexpected locks and errors, and is well worth a try if you really don't want to shut your machine down for some reason.