You might want to validate your CSS and your HTML.
I see numerous errors like this one...
Code:
Warning: Error in parsing value for property 'top'. Declaration dropped.
Source File: http://www.mannmitstativ.de/
Line: 0
Furthermore tags are opened but not closed and so on. All this can lead to unexpected behavior.
And to test if it is the Googlemap addon, please disable the addon from your admin panel and check your blog again.