Problem with webmail address book

[paranoidcookie]

I have an ISP 1.0.7 (upgraded from 1.0.5). Running Debian 6.0.1

Webmail works fine, except that when I try and add an address to the address book following the "Take Address" option

I get the error

ERROR
This page request could not be verified and appears to have expired.
Go to the login page (at which point I am logged out).

I can add addresses by going to address book, just not via take address. Does anybody have any ideas?