sale order currently being proccessed by user

using VA02 to change for a particular sale order (not for all),

Sales document 82857 is currently being processed (by user DESPATCH) message appears.

i have checked, no user is login with this particular user-id and also no other user is using this sale order number.

same problem existing since last night only for this particular order. this order is of large quantity and i cannot delete this order or using another order because all other planning is depending on it. please provide solution to sort out this problem. thanks in advance.