I think Nein might be on to something. As Nodsu said, check the CPU utilization.
Check the CPU utilization on the servers and on the PC's both when you are having problems and when things seems to be OK.
Also, check the event logs on the server for error and warning messages pertaining to network, authentication, and your specific app. The program may have been written to write messages to the event log. You may also want to check the event log on the machines that are exibiting the errant behavior.
Does the problem only occur on a select few machines, or all of them?
well since ABAMOTO does not use a program through a browser client
maybe it is how many client license's on machines?
What do you mean by client licenses? The only client licenses that will cause connection problems in a Windows environment that I know of are terminal service CALs. If you are running terminal services and have machines that do not have a CAL or aren't already built in (Windows 2000 have built in CALs for Windows 2000 Terminal server) those machines will not be able to connect to the terminal server after the Temporary license expires. I think Windows temp CALs expire in 120 days.
also ,a question ,why even run a server if it is setup as closed network
I don't understand this question. All client/server applications use a server.
if need a server for web app's keep that OS seperate from the
other one. no mention how the app run's
Sorry, I don't understand this either. What do you mean?
how ever if the clients are using an internet connect from somewhere other then the local net( dsl or dialup)
the server is still using or could use a cacheing system ,I would think it depended on the app ,needed to access.
The server would have to be the local machine's gateway for caching to work. Or there would have to be some serious server side DNS changes to route that traffic to a caching server. Traffic on a lan stays on the lan until it can't find what it's looking for. Then it sends traffic to the default gatway. Regardless of the internet connectivity. You are correct in that an application has to specifically support caching to do so.
I use access as data base and all static info is cacheable
What static info is cacheable? I'm curious. I've never used caching with access.
is the app running on it's own built in server
do they (client) need to log in with password is the password set tp expire
If they work at all then there isn't an authentication issue. If the password expired it wouldn't let them into the app ever until the password was reset.
one thing to check all the nics should be the same for dynaminic ip
or they all should be set to same speed and duplex
This is probably not the issue as they can access other files on the network. The problem seems to be application specific, but it may be worth checking out.
Another thing to do is to plug the server into a different switch if possible, or another port on the same switch. I still think the issue isn't your network, but rather the app that you're running. Do you know if the app has any updates? Is your server up-to-date? Definitely check the Logs and processor utilization on the server.
Any news on this ABAMOTO? I'm curious if you've found your problem, and what it was/is.