Downloading jars from MavenCentral does not work at my company.
As I understand, Ivy is used to handle repositories. I could trace the problem down to the fact, that Ivy (out of the box) does not work either, due to problems with the proxy and checksums.
I could fix the Ivy problem by forcing md5 checksums to be used in the ant script:
How can I do this configuration of Ivy in gradle?