I had to move my laptop over to the study, and we have an old/spare monitor which we haven't used a while - the last setup that used it was a CLI only linux install - it didn't flicker much, and text was sharp.
I decided to use it with my laptop (thinkpad r61, running a plain vanilla install of windows 7 professional with none of the lenovo addons) as a secondary screen - it seems to almost imperceptibly flicker, and text looked kind of 'off' (images seemed ok).
I'm guessing part of the problem is cleartype which IIRC is being used on windows 7. The flickering on the other hand...
I only have one monitor frequency available to me - 50 hz - there's no mention of what res or frequencies the monitor supports, so i'm unsure if that's the problem. All LCDs i have run at that frequency fine tho.
It could alternately be old age - do CRTs tend to flicker when they get older?