Comment 5 for bug 818642

Same issue for me. Gedit is randomly a lot unresponsive to the keyboard while typing. This never occurs right after Gedit is opened, I have to typed at least bit before it happens.

Occurs on Ubuntu Precise (12.04) while editing Ada source files (small files). Was not so much slow on Ubuntu Maverick.

Tried Medit, which does not suffer from the same issue -but which suffers from others issues), so don't believe it is due to the syntax highlighting, as as‑far as I know, Gedit and Medit use the same framework for syntax highlighting. Or else, if it's really due to syntax highlighting as some one above suggested, may be regex based syntax highlighting is not a good idea.