When I try to search Google Trends...
http://www.google.com/trends?q=hello&ctab=0

... I get this:

<<We're sorry.

The server encountered a temporary error and could not complete your request.

Please try again in a few seconds.

If this problem keeps happening, please email labs+trendsgoogle.com and mention this error message. >>

works fine for me Philipp :/

Humm. It's back for me too. Thanks!