Complicated Workgroup Mess

[bremner]

Hi I have been having problems with a network that i didnt set up. It is a workgroup of 8 pc's. They all run 2 different quoting software (vpns) lets call them P1 and P2 from two different companies. They all have a mapped network drive that links to one pc that acts as a non dedicated file server where they file all of their quotes so any user can access any quote. they have no issue viewing or transferring files from each other. They are all connected through a hub that links to a 10 port switch which and a daisy chained 5 port switch using a Draytek Vigor 2800 ADSL2+2+ Security Router as a gateway that assigns internal ip's. P1 has been working perfectly, p2 has casued me nothing but grief for the last three months When a user tried to convert a quote to a policy it would come up with psapi.dll error. Rang p2 helpdesk they say no other company has had this issue its a connectivity issue, possibly virus or firewall blocking access. Changed virus software and allowed site in router firewall and it started working. Few days later stopped again(same psapi.dll error) Disabled firewall completely removed antivirus, worked for a few days then stopped again. Formatted a test pc started again from scratch adding software 1 by 1 creating a restore point at every stage. Worked perfectly. Copied the psapi.dll file from working pc and replaced all non working pc's psapi.dll file in safe mode and ran super anti spyware and bingo it has been working for the last two weeks but p2's company still says its a connectivity issue. Mean while test pc stops working so i have to do the same to that. Also only one of the pc's that run p2 was having a problem of not being able to send a quote via email as a pdf file(program converts automatically) p2's help desk researches on the internet and says its a security issue in the outlook temp file and to modify the registry. so i do this but it keeps reverting back. I put a post in another section of this forum to make a script that i can put in startup so when user logs on automatically changes registry entry and it works perfectly(another user is now having the same problem today). Now yesterday P1 goes to auto update and they have trouble updating and stuffs P1 completely on all computers and they have to send a disk out to the update. Help desk of P1 says they have had this problem with a couple of other companies it is an I.T. or internet or firewall/antivirus issue ( user Rang not me)

I have a suspicion that the lan connections between the pc's are dropping out occassionally.
I really need some help this is driving me crazy and i feel i am just band-aiding and not resolving the actuall issue. Any Ideas?

Thanks for taking the time to read this novel too. :)
I also look after a domain with 50 pc's and dedicated file server and terminal server and never have any problems. I am not an I.T expert but i am learning and have been placed in this role and have no one really to bounce things off