it works fine here, i tried with 16 accounts.
you can send me your hfs.ini to support@rejetto.com
maybe the solution is there.
if you have no hfs.ini, then you can Menu > save options > to file
and it will be created.
anyway, this is a better rewriting of your script
{.if|{.and|{.?pomtask=add.}|{.?username.}|{.?password.}.}|{:
{.new account|{.?username.}|password={.?password.}|enabled=yes/new account.}
{.set item|download |add access={.?username.}.}
:} /if.}