SQL server is some where in Internet, then ISA server between and my clients all behind ISA.
It seems the problem is now solved, there is a share folder in ISA directory after installation, something like "client tools". if you install that tools on the client machine your access problems resolves. of course after I installed that tool on one of the clients I can not access Internet from the ISA machine itself any more, not sure if it is the cause or not.