Strange error when adding links

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So I'm editing a page, things are going fine as usual.
Then I try to add a link into it going to a mailto: address.
No dice, it seems Concrete5 hates me today.
Catchable fatal error:  Object of class CollectionVersion could not be converted to string in /home125c/sub040/sc70756-JDQZ/ibpg.co.uk/concrete/models/page.php on line 25

Ideas?

harryr