KEYBOARD LOCK??

I have an HP Probook 4540S operating on Windows 7.  Every so often I will be typing a document or working with the keyboard and it 'freezes'.  For example, I will be drafting an email and all of a sudden I cannot type numbers (it enters the symbol above the number) and when I try to click into the body of the text, it selects everything below the spot that I click.  Is there a button/tool for this?  Am I accidently pressing something that i don't know about?

Thanks!