now i've lost my horde login screen :'(
its all white , what can i do, all my emails

I am not sure what is going on with your install. I have run this script multiple times concurrently on the same server and haven't seen this type of behavior. What version of PHP are you running? If it's not the version per the script, then I suspect you probably need to update some pear modules. What do your logs say when you try to get to webmail? Without seeing your logs, you could try this:
pear install Log
pear install Date
pear install File
pear install Mail
pear ua
And see if that corrects the issue.
Per your previous post, there is a cron job that calls the reminders.php script for any calendar reminders. Your cron job could have been trying to run during the install.
Next, you could get radical if needed. In the root directory there should be a horde20-restore directory with a script you could run that should revert you back to horde20. This is provided you have an horde.old directory. To tell if this is the horde20 stuff, you can change to that directory and see if you have an ingo or mimp directory. You shouldn't have these directories because they are not part of horde20. If that works, then you could run the script again to upgrade.
Finally, if necessary, you could delete the horde directory entirely, then run the script again. This will cause the horde table to be dropped and you will lose any preference settings, calendar events. etc.
That's all I got,
JB