odd problem

Dear Sir,
I use emc2.4.7 in ubuntu 10.04 LTS for a long time.By accident I found an odd problem.After I use the "F3"&"F5" to change the Manual and MDI interface frequently,the MDI command edit can't be input the code.the accel key ("F3"&"F5" )also become invalid.Can anybody help me?Thanks a lot.
PS:when I update the emc2.4.7 to Linuxcnc2.5.4,the problem remains unresolved.

you need to move on to 2.7 , ubuntu 10.04 is now old and past support , so at some stage your going to have to upgrade to debian & 2.7 .
as your using 2.5.4 i presume your using an old pc , you would be best to resolve and update your hardware
amongst also have the advantages of the newer functions .

trying to support ubuntu has now stopped , in favour of debian wheezy , and the newer jessie shortly
updating will solve your problem .

That said, I still have a machine running on its original Ubuntu 10.04 installation which started on (emc2)2.3 and is currently running 2.7. So you may not have to update your OS or hardware inorder to update to 2.7. (At least not at the moment.) That machine of mine relies on an old ISA card for I/O, and I am not looking forward to the day that I must update its hardware.

Have you tried downloading and booting from the current live / install image and see if the problem persists in the current version?
linuxcnc.org/docs/html/getting-started/getting-linuxcnc.html

Rick G