type cast from bytea to varchar or whatever

Dear list,

in dbmail there's a query that worked until postgresql 8.2 (i stripped 
the unneeded parts for other tables):

SELECT k.messageblk FROM dbmail_messageblks k WHERE  k.messageblk ILIKE 
'%multipart/encrypted%';

In 8.3, you get an error 

[ERROR:  operator does not exist: bytea ~~* unknown LINE 1: ...55) ILIKE 
'%multipart/encrypted%' OR k.messageblk ILIKE '%mu...
                                                             ^
HINT:  No operator matches the given name and argument type(s). You 
might need to add explicit type casts.

OK, but how to cast that? messageblk is of type "bytea", so I can't use 
these:

SELECT k.messageblk FROM dbmail_messageblks k WHERE  k.messageblk ILIKE 
'%multipart/encrypted%'::bytea;
SELECT k.messageblk FROM dbmail_messageblks k WHERE  
k.messageblk::varchar ILIKE '%multipart/encrypted%';

any ideas?

(It should just convert, in case of special chars ignore them. The 
contect are mails, so normally text. Don't care about non-ascii here.)

mfg zmi
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