Hang ups on file server

[Blunted One]

So here is what is going on. When trying to access the file server on our network the folder will pop up that your trying to access but will basically lock up your computer for minute (more like 15 seconds). The folder will finally populate with the files, folders, etc and you can browse around without much if any delay.

Some computers never have this problem, but I am not sure what is so different about them as almost all computers in our office have the same configuration with hardware and software and all have Windows XP SP2.

I have tried to figure out if it is a firewall issue, anti-virus, network, etc. But still nothing seems to come together as consistent for why this is happening.

I want to blame our network, but then why would certain machines never experience this problem and others have it happen at least once a day? Even computers that are on the same switch as the file server (such as the boss's computer) experience this stop and go symptom.

Are there any settings in Windows or perhaps on the server that will delay your browsing of network folders?

I also noticed on the affected computers that it takes a long time to open a link to a folder on the file server that is sent in an email. The system will start to open the folder, then halts and basically stops responding and about 15 seconds later your back to normal again and everything moves quickly.

I am really out of ideas as to its cause...can anyone help or had similar issues with a file server or just any network browsing in general?