We have also had similar issues with the functionality used to update the scroll.style.height property. If you can debug the code check what value $x holds, in our implementation it is holding a negative integer which I think is whats causing the invalid argument exception.

Yes, you're right: $x = -36

I'm going to have to roll back to v6.4.2276, which is the last version that worked for me.

I think I've found a possible workaround.

In my page, I'm hosting the Scheduler control within a jQuery UI Tabs control, with some script to make the tabs take up the full height of the page (excluding the header). I hadn't set an initial height for the tab pages, since it's not needed in Firefox or Chrome, and prior to v6.6 it wasn't needed in IE8.

I've changed the definition of the tab pages from: <div id="tab-schedule">
to: <div id="tab-schedule" style="height:400px;">
and it seems to work (at least in IE8 mode from IE9).

I'm working on a a fix. It should be already fixed in the Calendar in the latest sandbox build (6.6.2355).

See also:
http://www.daypilot.org/sandbox/