What's wrong with the HTML Editor?

When editing the HTML of my project, when I put the cursor into position the text at that point partially disappears - notice the 'd' in 'bold' above. It's also slow and generally just difficult to use because the text gets so messed up when you edit it, that you can't see what you're doing!!
Trying to insert javascript is an absolute nightmare.
Is it just me or do other people have this issue too?
