validity check - registration name

I am using Joomla 1.0.8
SMF 1.1 RC2
Joomla-SMF component 1.1.4.2
Login Module 1.4.2

I have a problem every so often where users dont read the registration page and try to register with invalid characters or spaces in the username and the system doesnt reject them.

When I run the sync tool between joomla and SMF i get a few errors at the top of screen telling me that users could not be synced and the names it quotes either have dashes, spaces or other characters that are not allowed or in a few cases they were two letter usernames which is less than the 3 character minimum.

The messages read as follows ....

xxxxxx-xxx : Failed : Please enter a valid Username:. No spaces, more than 2 characters and contain 0-9,a-z,A-Z
xx : Failed : Please enter a valid Username:. No spaces, more than 2 characters and contain 0-9,a-z,A-Z
xxx xxx xxxxx : Failed : Please enter a valid Username:. No spaces, more than 2 characters and contain 0-9,a-z,A-Z

I thought perhaps that the problem might be 'old' users who had registered prior to me using the component/module so i purposely went and registered a new test account using a dash in the middle of it.

The sync tool tells me that the username is invalid, but the registration screen tells me I have registered and should receive an email soon ...

I have adjusted the language file to display username guidelines when registering, but we all know that most users wont bother reading that !!! Is there something I am missing either in Joomla, SMF, or the component that will actually reject the registration when submitted and display an error to the user ?