kernel panic on umass drive

[Xian]

I have small USB flash drive that has worked quite well up until now with 
FreeBSD. I've found I have to boot with it plugged in as when I don't will 
give a line in dmesg:

umass0: Generic USB Flash Disk, rev 1.10/1.00, addr 5

but it only give the lines 

umass0: Generic USB Flash Disk, rev 1.10/1.00, addr 5
da0 at umass-sim0 bus 0 target 0 lun 0
da0: <Generic USB Flash Disk 1.00> Removable Direct Access SCSI-0 device 
da0: 1.000MB/s transfers
da0: 31MB (63904 512 byte sectors: 64H 32S/T 31C)

I found that when I didn't have the da0 lines (It wasn't in the machine on 
boot) and I pulled the drive out it the kernel panicked about a page fault. 
The instruction pointer was 0xc0489e5b, and current process was 31 (irq21: 
uhci0 uhci1*).

[ian at hercules:~] %nm -n /boot/kernel/kernel | grep c0489e5
c0489e50 t uhci_check_intr
[ian at hercules:~] %uname -a
FreeBSD hercules.codepad.net 5.3-RELEASE-p4 FreeBSD 5.3-RELEASE-p4 #6: Fri Jan 
14 23:59:29 GMT 2005     
root at hercules.codepad.net:/usr/obj/usr/src/sys/HERCULES i386

Also a yesterday I compiled in "device ehci" and the kernel panicked on boot 
when just after it had detected umass when the drive was plugged in. So I 
compiled it out again.

I have had other USB Flash drives work properly on earlier version(s) of 
either 5.2.1R or 5.3R, I can't remember.

I'm not sure how to get round this, or who this information would help. Any 
help will be very much appreciated, or who to send this info to.

-- 
/Xian

"Too many of us look upon Americans as dollar chasers. This is a cruel libel, 
even if it is reiterated thoughtlessly by the Americans themselves."
Albert Einstein