I am close to going nuts with my tablet's input panel!

Since I have to write in different in different languages I constantly have
to switch input languages on my tablet. This (so far) relatively little
nuisance is developing more and more into a nightmare! Not only does this
fine piece of SW suddenly not memorize the input language from one
occurrence to the next, lately it occasionally even refuses to let me change
the input language! I.e. I see and can open the language list (the rightmost
menu in the input panel) but if I pick an entry nothing happens! This makes
using the tablet almost impossible!What could cause this frenzy?

Michael