[Testbed-admins] Problem starting experiments

wrapper line 418.

--------- /usr/testbed/expwork/ primotestbed/4thexp/startexp.2zwPnj --------
Running 'tbprerun -e 14 4thexp.ns'
Beginning pre run for primotestbed/4thexp. 22:43:58:851688
Running parser ... 22:43:59:816150
Parser done! 22:44:04:775796
Precomputing visualization ...
Image rendering proceeding in background mode ...
Setting up static routes (if requested) ...
Generating topomap ...
Verifying parse ...
Doing a pre-assign ...
assign_wrapper improved started
TIMESTAMP: 22:44:11:996492 assign_wrapper started
TIMESTAMP: 22:44:12:2689 TOP started
*** ERROR: assign_wrapper:
*** Can't call method "class" on an undefined value at
*** /usr/testbed/libexec/assign_wrapper line 418.
Cleaning up after errors.
Killing the renderer.
Removing experiment state.
*** ERROR: tbprerun: assign prerun failed!
*** ERROR: batchexp: tbprerun failed!
Cleaning up and exiting with status 255 ...
Running 'tbend -f -e 14'
Beginning cleanup for primotestbed/4thexp. 22:44:14:365679
Clearing out virtual state.
Removing visualization data...
Cleanup finished! 22:44:15:307686
**** Experimental information, please ignore ****
Session ID = 230
Likely Cause of the Problem:
Can't call method "class" on an undefined value at
/usr/testbed/libexec/assign_wrapper line 418.
Cause: internal
Confidence: 0.6
Script: assign_wrapper
**** End experimental information ****

--------- 4thexp.ns --------
# This is a simple ns script that demonstrates loops.
set ns [new Simulator]
source tb_compat.tcl

set maxnodes 3
set lanstr ""

for {set i 1} {$i <= $maxnodes} {incr i} {
set node($i) [$ns node]
append lanstr "$node($i) "
tb-set-node-os $node($i) FBSD-STD
}

# Put all the nodes in a lan
set big-lan [$ns make-lan "$lanstr" 100Mb 0ms]

# Go!
$ns run