Comment 7 for bug 665943

This does not only happen to applications run as root (like Synaptic) but also user applications, like Guake, mentioned above. It happens even on Mint 9, if you download the theme manually. Not sure if this is related, but the Mint-X and Mint-X-Metal theme also causes GCstar to freeze: https://bugs.launchpad.net/linuxmint/+bug/710509

The "flat-buttons" and GCstar problem do not happen with any other theme I've tried, including the ones from Bisigi. This is why I think it's safe to suspect that there is something particular within the Mint-X themes that causes this.