The remote host is missing an update to libgdata announced via advisory DSA 2482-1.

https://secure1.securityspace.com/smysecure/catid.html?in=DSA%202482-1

Vreixo Formoso discovered that libgdata, a library used to access various Google services, wasn't validating certificates against trusted system root CAs when using an https connection. For the stable distribution (squeeze), this problem has been fixed in version 0.6.4-2+squeeze1. For the testing distribution (wheezy), this problem has been fixed in version 0.10.2-1. For the unstable distribution (sid), this problem has been fixed in version 0.10.2-1. We recommend that you upgrade your libgdata packages.