[TYPO3-project-seminars] Submit button leads to start-page without submitting data

[Uli Linn]

Hi List!

In general, the seminar-extension works perfect. But there is one user, 
who can't register. Probably someone can give me a hint, where to search 
for a solution.

1.) FE chooses Seminar and clicks on "register"
2.) Login-Screen is shown, user logs in
3.) Registration form is shown, user chooses several optinons like food, 
lodging etc.
4.) user clicks on Submit button
5.) Usually, a confim page is shown and the data submitted, but this 
user is immediately redericted to the login-screen (2.)
6.) in the backend there is no registration data of this user

For all other useres, everything works as expected.

The user has a common setup with WIN XP SP2 and Firefox 3.5.5 with no 
manual change of the standard cookie handling, script acceptance etc.

Im using T3 4.2.10 with seminars 0.8.3

Has anyone an idea, what could be the reason for this strange behaviour? 
   I can't reproduce the error, but the user has ducmented each step 
with screenshots so I don't think that he did something wrong (what in 
most cases likes this is the reason why ...).

Thanks a lot for your help!

Uli Linn