I am having an issue with the Member Of field on the contact Module.

When I go into the contact that is already created and select an account to link it to from the "member of" field it seems to overwrite my primary address information upon selecting the account. Is this some undocumented feature?? I find it really annoying as I have contacts which do not have the same address as the account its linked to. Any help would be appreciated perhaps I have something wrong.