gbde and fsync

[dot at data.pl]

Hello,

When I try to unmount my bde device i get:

umount: unmount of /usr/home/PRV failed: Resource temporarily
unavailable

and (for example):

fsync: giving up on dirty: 0xc1c8ee70: tag devfs, type VCHR, usecount
1151, writecount 0, refcount 31, flags (VV_OBJBUF), lock type devfs:
EXCL (count 1) by thread 0xc1a3ce10 (pid 1608)
        dev ad0s3d.bde

I belive that drive isn't physically damaged and it worked fine for
months. But now it happens almost always when I work with large
(megabytes) amounts of data.
My system is: FreeBSD 5.3-STABLE #13: Fri Dec 3 20:20:36 CET 2004    
root at ALEPH:/usr/obj/usr/src/sys/ALEPH i386
but problem occured circa three updates ago. I really don't know which
informations could be important to diagnose.

Please let me know if You have any idea how to safe my data (beside
backup) and cleanly shutdown system or where my problem lies.

Michal Bartkowiak