To describe it in a few words: I have an Image Layer as overlay, defined with 0.5 opacity. After zooming in to zoom level 11, the image becomes opaque. After that point, there is no way to change the opacity other than reloading the page. This happens only with IE8 (and I am sure with IE7, too).
I prepared an example at http://jsfiddle.net/hc23n/ (the image is just for testing purposes). After zooming in you will see the problem. The strange thing is, that only the visible opacity is changing. If I type imgLayer.opacity; in the console it still shows me the right value. I tried to redraw the image and also the alphaHack, but there was not difference.
Does someone know this problem? Can it be solved??