Glide Keyboard not working after first use

Hi . i have a problema…
I have to fill a textbox , to do it i have used this instruction : windowUsernameAcquiredpwd.TapEvent += new OnTap(Glide.OpenKeyboard);

When i do it for the first time,all is working.
After i delete its content, go around in the gui, when i return in the textbox page i can’t refill it again.

It seems like the keyboard is locked, i can’t press anything…
someone can help me?

Thanks in advance

@ francoz - Can you post a small and complete example that shows the issue?