Vim on Ubuntu: Text rendering bug, repeating and disappearing weirdly

Question

I had vim installed on ubuntu 12.04 not long ago. Sometimes when I run my cursor (using keyboard, not mouse) over code, text disappears, as though there is a problem rendering t

Answer 1

So I found out whats the problem. Turns out after I removed one line from my .vimrc, the weird visual rendering bugs are gone.

Did not expect this innocuous looking line to be the cause:

set lines=50 columns=100

Not sure why this is the case though.