Can't add member to mail group

[breun]

I have a mail group with 57 members and want to add another member. When I click the 'Add New Member' icon the next page never finishes loading. Anywhere I can look for an error message?

This is Plesk 7.5.4 on FC3.

Edit 1: my whole Plesk session seems to hang when I click 'Add New Member'. Tested this on both Opera 9.01 and Safari 2.0.4. Both used to work, so I guess something is wrong with this Plesk installation.

Edit 2: Plesk also hangs when trying to add new members to other mail groups.

 

[breun]

An upgrade to Plesk 8.0.1 fixed this problem in the process.