zfs: allocating allocated segment

Hello,

this is my first mail on this list, please excuse my bad English :)

I'm running a File server with zfs, 64 Bit, 4 GB Ram and RELENG_7. Two days 
ago i uploaded a file via ftp to the server and the server is crashing. After 
reboot FreeBSD can't import the zfs-pool. There is a kernel-message:

panic: Solaris(panic): zfs: allocating allocated 
segment(offset=123456... size=74)

cpuid = 0
Uptime: 14m22s
panic: bufwrite: buffer is not busy???

Now i try to import the zfs-pool with a recent 8.0-current but with the same 
result. It's very important to me to access the pool, so did you have some 
idea's ?

Greetings,
Michael