Thanks.
I checked and found out that there has been an update for the PayPal Plus SSC Plugin, that is used on this site. After installing it, the bug seems to be fixed. Just in case someone else stumbles upon this post and it might help.
Coming back to my "harsh" reply I'd like to say that a text like
"Now he knows - he won't get the right answer and next time he'll think about what information to write - it will be a lesson for the future"
doesn't sound very polite even decorated with a smiley (and I am definitely not squeamish).
I really thought that I had the most relevant infos in place and described the problem short - I apologize for not writing in prose.
Not having several hundred posts on this forum doesn't mean, that I'm a beginner. I'm Joomler from the beginning earning my money with and around JOOMLA! since 2006. Yes Jörgen, I have customers and yes, they pay me and appreciate my work anyhow.
And yes, I know that the support here is done by yolunteers. Btw I am active as a volunteer in some JOOMLA! forums too, helping colleagues and newbees to gain their knowledge and skills...
Cheers and have a good one!