[TYPO3-seminars] seminars and PHP 5.4

[BENCH Artwork]

Hi,

after updating PHP from 5.3 to 5.4 I've run into problems with seminars and ameos_formidable. As soon as i click on a registration link i get following error
#1: PHP Runtime Notice: call_user_func() expects parameter 1 to be a valid callback, non-static method tx_dhstd::loaded() should not be called statically in typo3conf/ext/ameos_formidable/api/class.tx_ameosformidable.php line 2383 

if i set displayErrors = 0 the registration works, but after submit on last step i get the error message_wrongSeminarNumber_formal "There is no event with this number. If you get this error message using a link on this page, please notify the webmaster. Thank you!"
The registration will complete correct in the system.

i use 
TYPO3 4.5.33
seminars 0.9.91
onetimeaccount 0.9.0
ameos_formidable 1.1.549

Any help?
Thanks!