Invoice workflow "No Approval available"

Hi Guys,

I have an issue with custom invoice workflow...when an invoice is created and a approver is added via add approver...after adding those approvers....the approval preview shows those added approvers as to be approved by...but after posting the invoice...if i see the approval preview...i can see that both added approvers node doesnot reflect the names of the approvers inspite it is showing 'no approver available'....in those added nodes.....and the workflow didn't start....this whole scenario happens...randomly..when user tries to add an approver....

we are in SRM5.0 sp SAPKIBKT06

Please help me out to fix the issue....

Full points will be awarded...

Thanx in advance,

Radha