The question I would ask you is do you really have a lot of users that use Mac-IE5.2?
I ask this mainly because IE for Mac is a horriable program that acts totally differen then Windows IE, also the latest verison is 5.5.
I personally run a web site that is for educational purposes, I get almost 400k to 500k hits a month. In a month I will get MAYBE 1 or 2 hits from IE 5.5 for Mac(July I got 0). So for me, if someone is using IE for Mac, I could care less if everything breaks(which I don't even know if it does or not).
So really you have to think about who is going to viewing this web site and what they are viewing with.
As for your problem. No idea since I've never programmed for IE4Mac 5.2, but I'd guess you are using something that is not supported by it, since it's old .(obvious answer) ;)