Unable to launch installer after downloading update

After installer was downloaded I press "Start update" and get message "Unable to launch installer, try doing this manually"
I`ve just migrated to Win7 x64, so problem can be caused by this.
Also destination path has Cyrillic symbols

In build 1535 an improved launcher was introduced when performing the upgrade installation, we wont know if this new method works better until the next build is released.

Please disable UAC as UAC may interfere with live update and UAC also serves no purpose other the to annoy ppl.

Also I notice this is yet another post by you for same issue which has been answered.