Is that a MySQL Db, resulting from a recent move, right?
You're lucky , just saw something like that very recently. You need to set the homepage field to NULL, for those where there is no value.
Probably the SQL query should be something like this:
UPDATE FORUM_MEMBERS SET M_HOMEPAGE=NULL WHERE M_HOMEPAGE=''
Try it and let me know if it works.
P.S.: You had solved it before, didn't notice it, sorry.