There was one major change between 3.5 & 3.8, The hard-disk size was increased to 64GB (This happend in Home 3.7).
Which made it incompatible with previous versions, so when you un-install YouWave you have to be absolultly sure there are no residual files in the following directories:
%USERPROFILE%\.Virtualbox
%USERPROFILE%\youwave
C:\Program Files\YouWave Android
After you made sure the directories are empty, restart your computer before re-installing youwave.