disk alert for sun cluster global device

I am running xymon 4.2.3 on sun solaris and find that the 'disk' test for my sun cluster clients' global devices does not report panic levels properly. e.g.:

  Mon Dec 7 10:42:58 CST 2009 - Filesystems OK

Filesystem kbytes used avail capacity Mounted on /dev/md/myhost-global/dsk/d33 36144364 18446744073708170202 37164335 51551811753178% /archive

The same client also has Big Brother running and correctly reports:

red Mon Dec 7 10:45:42 CST 2009 - Disk on myhost at PANIC level

/archive (51551811753178%) has reached the defined disk space PANIC level (95%) ... /dev/md/myhost-global/dsk/d33 36144364 18446744073708354634 36979903 51551811753178% /archive

any ideas?

thanks