AWS SDK gives error code 400; bad request

I am not sure since when, but on my development machine I get the following error using the AWS SDK with Java:

2015-02-24 18:57:05,834 DEBUG ~ Receiving response: HTTP/1.1 400 Bad Request
2015-02-24 18:57:05,834 DEBUG ~ << HTTP/1.1 400 Bad Request
2015-02-24 18:57:05,834 DEBUG ~ << Server: nginx
2015-02-24 18:57:05,834 DEBUG ~ << Date: Tue, 24 Feb 2015 18:57:05 GMT
2015-02-24 18:57:05,834 DEBUG ~ << Content-Type: application/xml
2015-02-24 18:57:05,834 DEBUG ~ << Transfer-Encoding: chunked
2015-02-24 18:57:05,834 DEBUG ~ << Connection: keep-alive
2015-02-24 18:57:05,834 DEBUG ~ << Bucket: "testmedia"
2015-02-24 18:57:05,834 DEBUG ~ << Accept-Ranges: bytes
2015-02-24 18:57:05,834 DEBUG ~ << Age: 0
2015-02-24 18:57:05,834 DEBUG ~ << X-Cache-Hit: No
2015-02-24 18:57:05,835 DEBUG ~ Connection can be kept alive indefinitely
2015-02-24 18:57:05,835 DEBUG ~  << "51[\r][\n]"
2015-02-24 18:57:05,835 DEBUG ~  << "<?xml version="1.0" encoding="UTF-8"?><Error><Code>InvalidArgument</Code></Error>"
2015-02-24 18:57:05,835 DEBUG ~  << "[\r][\n]"
2015-02-24 18:57:05,835 DEBUG ~  << "0[\r][\n]"
2015-02-24 18:57:05,835 DEBUG ~  << "[\r][\n]"
2015-02-24 18:57:05,835 DEBUG ~ Connection [id: 8][route: {s}->https://testmedia.xxx] can be kept alive indefinitely
2015-02-24 18:57:05,835 DEBUG ~ Connection released: [id: 8][route: {s}->http://ift.tt/1ApUNVo kept alive: 1; route allocated: 1 of 50; total allocated: 1 of 50]
2015-02-24 18:57:05,836 DEBUG ~ Received error response: com.amazonaws.services.s3.model.AmazonS3Exception: null (Service: null; Status Code: 400; Error Code: InvalidArgument; Request ID: null), S3 Extended Request ID: null

I can upload the file, so the credentials seem ok, but I don't seem to download it. I am using the Play! Framework (1.2.7) running JDK 1.7 and the AWS SDK 1.9.17.

What could be the cause of this?

It is recently that I did switch from JDK 1.6 to 1.7 because of a signing issue on 1.6 with AWS. I don't have it (yet) on my production servers, so it might be OS X related, but don't dare to deploy my code to production until I know for sure it will not break.