User not copied across when synching.

I added a student to a course that I already had setup with server client synching. I added the user to the server and then assigned the student the role of student in a course on the server. I then updated the course and found the user didn't copy across.

I did get errors.

When backing up the course on the server I got the error
Name: backup-srv103-20080603-1641.zip

• Creating temporary structures
• Deleting old data
• Creating XML file
  o Writing header
  o Writing general info
  o Writing course data
  + Course info

Notice: unserialize() [function.unserialize]: Error at offset 0 of 6 bytes in C:\projects\VLE\Mobile Moodle\environments\xampplite-win32-1.6.6.exe\development\offlinemoodle-0.4\htdocs\moodle-server\backup\lib.php on line 534
+ Blocks
+ Sections
o Writing users info
o Writing categories and questions
o Writing scales info
o Writing groups info
o Writing groupings info
o Writing groupings-groups info
o Writing events info
o Writing gradebook info
o Writing modules info
+ Choices
+ Databases
+ Forums
+ Glossaries
+ Labels
+ Lessons
+ Quizzes
+ Resources
o Course format data

• Copying user files
• Copying course files
• Copying site files used in course
• Zipping backup
• Copying zip file

and when updating on the client I got the error

Notice: Undefined property: stdClass::$original_wwwroot in C:\projects\VLE\Mobile Moodle\environments\xampplite-win32-1.6.6.exe\development\offlinemoodle-0.4\htdocs\moodle\backup\restorelib.php on line 2357