SAP popups hang in Linux client

Hi experts,

We installed SAPGUI for Java 7.20 on some of our client machines having UBUNTU 11.10 OS platform.

Everything is working fine except some of the pop-ups (like F4 help popup, Calender popup or Variant Selection popup) are getting hanged after selection.

Please suggest to find the root cause of problem.

We have Application Server Installed on Win2003Enter.Edition.

Thanx in Advance.