IP Address problem

Hi,
I have a problem with IP addresses.
After a certain time some of the PC's on the domain cannot access the network. If I change the IP address it then works fine for a few days and then the same thing happens again.
It has only affected 3 out of 20 PC's.
It is as if the addresses expire and then cannot be reused with that PC.
The IP addresses are static.
Any advice welcome.

Can the other computers access these computers?
For twenty workstations would not a DHCP server be more efficient?

If you are using static IP's how are they expiring? If you are assigning these IP staticaly make sure to remove them from your available to lease on your DHCP server.

Sorry for not following up sooner.
Basically the reason we don't use DHCP is because the previous network manager prefered static.

I have no idea what is happening.
Everything works fine for a few days and then one pc on the sub net will get a log on error "No domain server available" etc. If I change the IP address to a new previously unused one everything works fine. Then the same thing happens again a few days down the line.
They are not expiring but something similar is happening.

Check the event viewer and see if a network/system event is being logged. When the IP address becomes `stale` see if you can see that computer from a computer currently on the network. Also see if you can net view when this happens.
...
If you are the network manager I really suggest you go DHCP.

Thanks for your reply.

The main reason for not using DHCP was because we have 3 external sites (2 UK & 1 Ireland) and 20 reps with laptops apart from the main offices.
So we use remote access quite a bit for problem solving. Having static IP addresses made it a bit easier.
As I said it is a heriditary problem but I may look into changing this in the future.

Did you get a chance to test out the suggestions I posted?

Problem Solved!!! (I Think).

The same thing happend again this morning.
There were no sygnificant event logs.
I think it was something to do with the lmhosts file.
Re-did the file and all seems well. Fingers crossed.

Thanks for you advice.

You should identify what process/event is writing to the lmhost file that would prevent network connectivity. This file is normally static and is not updated via an automatic process.

I don't think anything is writing to it.
When I tried lookind at the netbios remote cache name table (nbtstat -c) it was empty.

I removed all the entries in the lmhosts file and added the IP addresses, names, domain etc of all of the servers,
saved it and renamed the file in dos to remove the file extension and everything worked fine.

Not sure if this is the correct method for doing this but it seemed to work.
I'm not sure why the original lmhosts file would be a problem though.