Timo,
I upgraded from alpha3 to alpha4 yesterday, and I am seeing a few of the following asserts:
imap(user): file mbox-lock.c: line 379 (mbox_lock_fcntl): assertion failed: (lock_type == F_UNLCK)
Gdb info on a couple of the cores is attached. It looks like the arg lock_type for mbox_lock_fcntl() is not getting passed in correctly, like the enum "enum mbox_lock_type type" in mbox_lock_list() is not getting set or used correctly so that lock_data[type].func is wrong. Hmmm.
My setup: Solaris 9, mbox, dovecot built with gcc 4.0.2. The filesystem for INBOXes is NFS mounted from another Solaris 9 system, but the index files reside on local filesystems. My setting for "lock_method = fcntl", per your release notes. I did not change the default setting of "mmap_disable = no" because my index files are local.
Jeff Earickson Colby College