Nav freezes while applying customer entries

NazD

Hi,
Greetings!
We have 2009 installed for one of client.The 2009 NAV is opened via Citrix.Now this is unique issue only ONE user is facing.When she drills on the customer card balance and tries to apply customer entries and selects more than 1 and applies(f9) the system freezes.This behaviour is observed only sometimes ..Most of the times it freezes. As we are supporting this client we did the following steps
1.Checked user citrix profile-No issue found
2.Checked code -no validation written
3-Checked on sql-no blokcing process or any task running behind which may ask for user output which freezes the screen
4.Checked roles and permission-Another user has same roles but only issue is observed for this user

We have tried all and not going anywhere.User if frustrated and keeps on escalating
Kindly help.