Thin vertical yellow line on monitor

[Jase]

When I turn my computer/monitor on from cold, there is often a thin yellow line/strip running vertical down the monitor.. it disappears after a minute or so and is fine.

The monitor is a Dell 2408WFP

Just wondering what the problem could be? assuming it's the monitor is that covered by warranty (it's about 21 months old) ?

 

[EsaT]

You can rule out graphics card if you try monitor in other PC.
Just do that from "cold" because problem is clearly caused by something which disappears after warming up.