Increasing crawling errors through event calendar

Hello,
today I got a message about increasing crawling errors on my page. When looking to webmaster-tool I found about 900 sites with crawling errors.

e.g.
http://stieglerhaus.at/veranstaltungen/page/363/
http://stieglerhaus.at/veranstaltungen/page/350/
http://stieglerhaus.at/veranstaltungen/page/301/
http://stieglerhaus.at/veranstaltungen/page/691/

But these are sites I do not know and what can I do solve this problem.

Thank you very much in advance
Christoph

The page I need help with: [log in to see the link]