Domain mapping and Plesk

I have installed wordpress multi with the domain mapping plugin, but two things keep happening and I'm not sure how to provide a fix for it.

1) somehow everytime I try to point a new domain to the IP address of this install, plesk changes the default domain for that install and all my mapped domains go to a default plesk page instead of the appropriate blog

2) with new mapped domains, even though I point the domain to the IP with an A record, the mapping doesn't work. Each time I've had to call support to have them fix the problem until now they don't want to fix it any more (guess they are getting tired of doing it every time).

I know that some config files need adjusting but I don't know enough to know the exact problem. Can someone help point in the right direction? Someone also mentioned to me that this was a quirky Plesk issue. Has anyone found a permanent fix for this?