i also had the Ascii error, but finaly i got 8.4 (final) running...
1 -> deinstalled 8.3
2 -> deleted the postgresql data-folder (made a backup before)
2 -> installed 8.4beta2 with SQL_ASCII encoding
3 -> created a new HM-Database
4 -> imported all HH into the new Database
5 -> deinstalled 8.4beta2
6 -> installed 8.4 (final-oneclick) using the data folder from the 8.4beta2 installation (the one with the new database)
7 -> start HM -> success -> at least for me
you can try to skip the steps 3 to 4 and excecute them after step 6. should work too.