nnimap splitting emacs 24, does not split

[pramble]

After upgrading from emacs 23 to 24, nnimap splitting does not split.
Sorry if this sounds vague, but I would be so grateful for pointers as
to where to start looking.
>From the customize buffer, the relevant parts look like the section
below. I only post this, hoping it is more readable than the lines
from my .emacs file.

I have no problem collecting mail from three imap servers. Everything
simply goes into my INBOX.

I do not expect anybody to fix this for me, but do not hesitate to
tell me which variables I should set to get some more information.
I did have "default" before the start of the list below, but that did
not make any difference.
Many thanks for any advice.


Gnus Secondary Select Methods:
INS DEL Select Method:
            Method: Value Menu nnimap
            Address: muenchen
            Options:
            INS DEL Variable: nnimap-address
                        Value: "mailhost.uni-blah.de"
            INS DEL Variable: nnimap-server-port
                        Value: 993
            INS DEL Variable: nnimap-stream
                        Value: ssl
            INS DEL Variable: nnimap-inbox
                        Value: "INBOX"
            INS DEL Variable: nnimap-split-methods
                        Value:
(("INBOX.moocow" "From:.*moocow*")
 ("INBOX.spam" "from:.*knauer.net")
 ("INBOX.spam" "subject: .*symposium on neural networks"))