qmail-pop3d not handling enough messages

[Thomas Ackermann]

hy!
i've gat a qmail-system with vpopmail, using the qmail-pop3d as popper.
my problem is, that the number of messages in my cur grew up to 23240
and now i cant get them anymore, the pop3d gives out an error like cant
change to $Home/Maildir..

anyone help?
thx
thomas