Invalid Workflow: Bad session string

Nissan

We have a custom workflow that is working on our current TS Prod Box.

We recently installed TS same version on two Dev boxes and are in the testing phase.

The custom workflow gives a javascript alert:

Invalid Workflow: Bad session string (followed by session string number)

Could anyone please explain.

Tried the below:
1. As mentioned in the support site article, i tried renaming the worklfow dir in iw-store and restart and try but still got the same error.
2. Tried minimising the wft to just 2 task, a start cgi task and end task and tried but still getting same error.
3. Tried running the OOTB "/iw-bin/sample_cgi_task.ipl" but looks like it does not go till there. the workflow is failing much before reading the task.
4. Checked all user permission, groups and file permissions.
5. Tried the workflow with logging in as root user in TS - it worked fine but for any other user it is not working.

Not sure if i missed something.

Please advise.

TS Version on 2 Dev box: 6.5 SP3
OS : Solaris