Ok, I'm getting worried, I've got some weird vertical lines running down my display, as per the image:

It's a 19" Iiyama PLE1900WS fed from an ATi 5850 via vga cable (no spare one to rule this out, unfortunately).
The lines are spaced approximately 4cm apart.
They are present on the desktop and games, but haven't noticed them on BIOS/Windows loading screens.
Can anyone shed any light as to what's going on?
And should I be saving now for a replacement monitor?
Any feedback appreciated!

It's a 19" Iiyama PLE1900WS fed from an ATi 5850 via vga cable (no spare one to rule this out, unfortunately).
The lines are spaced approximately 4cm apart.
They are present on the desktop and games, but haven't noticed them on BIOS/Windows loading screens.
Can anyone shed any light as to what's going on?
And should I be saving now for a replacement monitor?

Any feedback appreciated!