running craftbukkit in background doesn't work

hi,
after a long time i decided to update my server. up till now i was running build 670 which ran fine so far. now i wanted to update to 1185 so i moved my old files to a backup location, downloaded the 1185 build and started from scratch.
logged in to my server using ssh, started the server with "java -Xincgc -Xmx1G -jar craftbukkit-0.0.1-SNAPSHOT.jar -nogui &" and my cpu load jumps to 100% and the console is flooded with ">>>>>>>..." log shows nothing.

so i started testing -> up to build 766 everything runs fine. starting with buil 798 this error occurs.
then i tried "java -Xincgc -Xmx1G -jar craftbukkit-0.0.1-SNAPSHOT.jar -nojline -nogui &" and get an only slightly different result: cpu load still 100% but instead of ">>>>>>" it spams "[INFO] Unknown command. Type "help" for help." which also appears in the log.

vanilla minecraft server works without error. running with no plugins doesn't change a thing.
when NOT running the server in background (without the &) everything works like a charm. but this causes the craftbukkit server to shut down when i log off so this is not very helpful.

system info:
FreeBSD mediasvr1.local 7.3-RELEASE-p6 FreeBSD 7.3-RELEASE-p6 #0: Fri Sep 2 10:03:40 JST 2011 [email protected]:/usr/obj/freenas/usr/src/sys/FREENAS-amd64 amd64
java version "1.6.0_07"
Diablo Java(TM) SE Runtime Environment (build 1.6.0_07-b02)
Diablo Java HotSpot(TM) 64-Bit Server VM (build 10.0-b23, mixed mode)

can anybody help me with this?