Panic in gptzfsboot?

I have just re-built world and kernel and get a boot failure:

panic: free: guard2 fail _at_ 0x412f6c50 + 513 from unknown:0
--> Press a key in the console to reboot <--

I'll try to boot from a memory stick, now, but wanted to let
others know, that there seems to be a problem with the latest
UMA code which may cause a boot failure at this early stage.

STefan