Hi Christopher,
I think that your VI may not have gotten attached. However, I went ahead and tried this and I was unable to reproduce it. I am running Win 2000 with an AMD 700 MHz proecessor. I have LabVIEW 6.1 with all the newest drivers.
I just opened a new VI, placed an intensity graph on the front panel, created a property node, and then created a Boolean control to set the "Blinking" property. I ran the VI a number of times, setting it back and forth between true and false. I never got it to hang.
Maybe it's something else inside your particular VI. Try to attach it again and we'll take a look at it. Cheers.
J.R. Allen