I have had the same problem. A solution is to go into the Virus Scan part of ZA, go to advanced, the turn off the "On Access Scanning". This will make it faster, but you will have part of your virus scanning turned off. MacAfee doesn't seem to have this problem.
I have had to go to another virus scanner because of this problem and also a conflict with the Verizon VZAccess program.
Also I have had a serious problem when I tried PCcillin.
See my other posts on these problems.