I am experiencing the same problem. Deskscapes will not download. I have a fully licenced and valid copy of ObjectDesktop Ultimate. I've tried using the "Reset Data" suggestion w/ reboot. I've uninstalled Deskscapes via Impulse w/ reboot. I've tried to restore my archived copy which failed. Trying to update from Deskscapes (available), I get the infamous error: "The beta of the application you are attempting to download/register is not available."
Specs:
Impulse version: 3.23.454 (Build 1304)
Your computer has a Windows Experience Index base score of 5.4
Your Windows Graphics Experience score is 5.9
WindowBlinds version : WindowBlinds 7.0 (build 230 x86 - Vista Edition)
WindowBlinds is installed correctly on this PC
WindowBlinds appears to be activated on this PC
(SyncMaster 931C, SyncMaster Magic CX930B(Digital)) 1 is attached to NVIDIA GeForce 7600 GT
Wblind.dll 2009/11/16 12:43:20
Wbsrv.dll 2009/11/12 09:19:07
SevenConfig.exe 2009/11/12 11:16:53
Wbload.exe 2009/11/06 12:44:12
Wbhelp.dll 2009/09/25 08:42:07
Tray.dll 2009/10/21 09:13:19
Wbload.dll 2009/09/25 07:41:28
Screen.exe 2009/11/07 12:39:26
Obviously, at this point Deskscapes is not usable. Any help in restoring it would be greatly appreciated. 
RESOLVED: In Preferences I unchecked the option to show pre-release (Beta) versions, clicked on the "Reset Data" button again and rebooted. After opening Impulse the available version for Deskscapes was changed from before and I was able to download and install it. I'm a little reluctant at this point to enable pre-release versions again although over quite a number of years I can't recall ever having this kind of problem with any of them.