Keyboard + mouse problem

Hi, everyone! I have a very annoying problem with my laptop - amilo pro v3505. My keyboard often acts very weird - when I type letters it responds as if I type ctrl+them, i.e. only shortcuts activate. I can't write text at all, but rather get an annoying sound. Also when clicking with the mouse on different icons, I get them marked or when I use the scroller the font size changes as if I hold the ctrl! After a couple of days the problem suddenly disappears for 2-3 weeks. I had the keyboard changed and I have installed different copies of windows xp and ubuntu, but the problem seems to persist. What should I do?