Hi Maike,
I am afraid I still do not have access to any of the Corel products, so testing at my end is not possible. The update to the libraries has been delayed considerably, although I do hope it will be done sometime this year :-)
From looking through our previous testing together, it looks like there was an issue with the symbol wrapper coming from Illustrator. In future versions, I will make sure there is a version which only contains the drawings without this wrapper, but perhaps your best bet at the moment would be to download a trial version of Illustrator from the Adobe website so you can access the symbols you need and transfer them to a format that you can use with Corel.
Sorry I don't have any better news at the moment.
Cheers,
Adrian