weird vertical linse in dual scan

[Sang H Kim <sk6k+@andrew.cmu.edu>]

I have a 755Cs dual scan thinkpd
and when I life the screen sometimes, the bottom half is filled with
vertical multicolored lines
all i  have to do is shift the screen a bit and it's gone. but it's
annoying and it never had that problem until 2 weeks ago.
is this a serious problem?

thanks in advance