Sorry for the weekend headaches everyone... The bug which was supposed to be fixed by the updated SDK was instead caused in reverse by the updated SDK. Unfortunately, it only happens on some systems, and builds so it tested as working initially.
A new ActiveHome PRO 3.301 installer is up now which will update the ActiveHome PRO side to the same version as the SDK side. Remember all ActiveHome installers now update all files and plugins, so this installer will update all of your currently installed plugins too.
The root of this is changes to x10net.dll, which we don't usually change much. Most of the recent activity has necessitated updates. I will look into ways to get the SDK to work with a wider range of versions, but for now the old SDK should work up to builds 281, and the new SDK will work with builds after 301 up to the next time the x10net.dll needs to be updated again. The next time it is updated, however, an SDK update will be much closer on its heels, since we now know this breaks it.
For those of you having uninstall issues, are you running x86 or x64 windows? In the meantime, the current installer creates the Program Files\AHSDK\ directory, adds a copy of ahscript.dll, ahcmd.exe, ActiveScript.exe, and Interop.ActiveHomeScriptLib.dll to the Program Files\Common Files\X10\Common\ directory, and does some basic driver installation. The drivers shouldn't effect the system, so by removing all of those other files from those locations you effectively undo the installation. As usual, Program Files may change based on your windows version. You need to stop the X10 network service before you can delete x10net.dll. Running SDK developed applications need to be closed before the SDK .dll files can be deleted.