Not sure if this qualifies as a bug… although it is’t good.
It seems the script based installs fails to install one (but important) package.
On a new system (vps) the quota rpm package wasn’t installed and interworx also didn’t install it with the shell script as it probably wasn’t listed as a dependancy.
Therefor any siteworx account could not be added.
We did fix it manually by a:
yum install quota quotacheck -cvugmf -F vfsv0 / quotaon -a