'Backingstore problem':

Thorsten Sandfuchs found some issues concerning backingstore. Problem arouse 
as you try to connect to a 0.5.0 installation with no 2.0.0 backend support 
and a 2.0.0-client. As Nomachine changed the behaviour of the 
backingstore-option. In 1.5.0-clients the client sends "always, 
when_requested" et all and freenx just passed this string to the nxagent-call. 
The new client now sends "backingstore=1" and the 1.5.0-nxagent issues a 
warning and an error with "no argument requiered for -bs" or with "Error: NX 
Agent exited with exit status 1.". You can read all his message here: 
Backingstore or 2.0.0-client and 1.5.0 backend and freenx-0.5

Look at nxnode and in function 'node_start_agent()' after this line

 [ -n "$backingstore" ] && B="-bs $backingstore"

add this lines:

 # backingstore = { "when_requested", "always", ... }
 
[ -n "$backingstore" -a "$ENABLE_2_0_0_BACKEND" != "1" -a "$backingstore" != "1" ] 
&& B="-bs $backingstore"
 # backingstore = 1 (new nxclient 2.0.0 doesn't send any strings in the 
option-string for backingstore anymore)
 [ -n "$backingstore" -a "$ENABLE_2_0_0_BACKEND" != "1" -a "$backingstore" 
= "1" ] && B="+bs"
 # backingstore = 1 and 2.0.0-Backend EXPERIMENTAL
 [ -n "$backingstore" -a "$ENABLE_2_0_0_BACKEND" = "1" ] && B="-bs 
$backingstore"

This works using nxclient version 2.0.0-98.

http://www.centos.org/modules/newbb/viewtopic.php?topic_id=4941