Hi, when installing the SMF on the same database as Joomla, should the table prefix for SMF stay as smf_ or should it be changed to jos_ (the joomla table prefix)

Hi, I am using Joomla 1.5.3 and JSMF 2.0 RC3.1.
The SMF installed fine and is installed on the same database as Joomla (smf_ table prefix)
When I go to configuration and click Patch Joomla Source Files I get the following error:

Catchable fatal error: Object of class JVersion could not be converted to string in c:\..\xampp\htdocs\joomla\administrator\components\com_smf\admin.smf.class.php on line 2073.

When I click Patch SMF Source files, it seems to work fine.
But when I click to Synchronize Joomla and SMF users I get the following errors:

Failed: Error verifying user synchronization.:db_error:Table'databasename.members doesn't exist SQL=Select count(*) FROM members LEFT Join jos_users ON jos_users.username=members.memberName WHERE users.username IS NULL1.

Can anyone help?