I just tried again to create a rescue USB and still get the massage:
http://www.screencast-o-matic.com/screenshots/u/Lh/1396038241730-88663.png
This function worked some month back when first introduced in a beta build.
http://youtu.be/vJ7oamXCwJA
When will this be fixed ? Preparing for a disaster needs to be done before the disaster happens. 
Yes! this problem should be fixed 
i had this problem too.
i was able to fix it by:
1.removing these in controlpanel what appeared after trying first time to create rescue USB
in Programs list.
Windows PE x86 x64
Windows Deployment Tools
Windows PE x86 x64 wims
2.removing Windows Kits folder in Program Files (x86)
3.removing AvastPEToolkit folder in My Files folder
after that it took about 5 min avast to download it and 3hours to install it.