[TYPO3-seminars] error after upgrading to 4.5.8

[Rene Gulager]

Hi sorry for cross posting but was not aware of this list dedicated to 
seminars.

I have upgradet to typo3 4.5.8 and the newest seminar and 
onetimeaccounts. When useres submit the registration form they get the 
following error:

Fatal error: Call to undefined method stdClass::fetchGroupData() in 
/srv/www/htdocs/typo3_src-4.5.8/typo3/sysext/cms/tslib/class.tslib_fe.php on 
line 673

The data in the url is:
/index.php?eID=onetimeaccount&data=YTo0OntzOjM6InVybCI7czoxNDE6Imh0dHA6Ly93d3cubGlnYS5jb20vdWRkYW5uZWxzZS91ZGRhbm5lbHNlL3JlZ2lzdHJlcmluZy9yZWdpc3RyZXJpbmcuaHRtbD90eF9zZW1pbmFyc19waTElNUJzZW1pbmFyJTVEPTYwJnR4X3NlbWluYXJzX3BpMSU1QmFjdGlvbiU1RD1yZWdpc3RlciI7czo0OiJ1c2VyIjtzOjIwOiJkaXZAcmVuZWd1bGFnZXIuZGstNSI7czo0OiJwYXNzIjtzOjg6IjZYYWVyYXhnIjtzOjM6InBpZCI7aToxODE7fQ%3D%3D

Any idea of what is wrong ?

Regards
Rene Gulager
Bitproduktion.dk