I have 19" Sony Multiscan G400, and although at it's time it was one of the best screens on the market, it started to go berserk after 4 years of usage. It's now 6 years old, and I can't use it for image editing, actually I can hardly use it at all - the colors are extremely washed out, the screen is flickering and changing colors from time to time, and at least once daily it turns itself off.
It's well known fact that after 3 years of usage, CRT monitors might start dying (I say might because although big percentage of them goes away, some can still be usable after evem 7-8 years). I don't know how old your display is, but since Sony ceased production of Trinitron displays in 2001, I guess it's quite old. I suppose it's time to invest in some good LCD display (Apple, Eizo, NEC...), but it really depends on state of your CRT display - if you're sure that colors are accurate and that you can do succesfull work on that Sony, then use it.
