Login Scripts not working using Active Directory

We have been using the same Login Scripts with AD for years. We use a simple BAT file to map network drives. We have five different offices which use the same script which is modify for each different location. As I said they have been working for years. Suddenly the login scripts are not working on random PC's. The problem is so random that it will sometimes work on one PC after a few reboots. I also have half of the PC;s not even having the problem. I've tried a bunch of different things but nothing seems to be working. To make it even stranger I can manually run the login script on each of these machines, it will just not randomly not run through login. Has anoyne else ecperienced these problems? Thanks in advance for your time.