slow response opening file by unc-path

After installing Arcserve 2000 AE with TLO and SAN-option and BAOF (and ie5.5 because else arcserve doesn’t work) on a NT4 enterprise server, I experience problems when I try to open a document on the server via an UNC-path from another workstation or server. It takes more then 30 seconds to open the document (txt, doc, htm or whatever). Opening the same document via a drive-mapping shows no problems.
I uninstalled ie5.5 to see if this would help, but apart from the fact that Arcserve doesn’t work anymore, it has not the desired effect. Also stopping all the Arcserve services is not the solution.
Does anyone have any suggestions where to look?