It doesn't seem quite accurate to say that there's a trendline from Nov '08 which has offered support to ITRI. Because there are only two points on this trendline that you propose...First the Nov '08 low, and Second the lows from this past week.
I bought ITRI at $67/share and am now underwater. I'm trying to decide whether to sell and look for support at the the 200 day MA below $60. But I would only buy back if the tone of the overall market improves later this month or even in March.