XPath string and xpath node are both null

[ratha]

Hi all,
When i deploy my BPEL process (with Eclipse BPEL editor), it says "XPath 
string and xpath node are both null".
But i haven't assigned any 'query' element in the to-spec of an "Assign" 
activity. All the 'Assign' activity i assigned to Fixed 
value-->Variable.(i checked several times)

Any help...

Thanks& Regards,
Ratha.