Apple has stopped signing iOS 8.1.1 meaning that it is no longer possible to downgrade or restore to the firmware.
Thankfully, we don't have to warn you not to accidentally update to the current firmware version, since we already have a jailbreak of iOS 8.1.2!
TaiG has released a jailbreak utility for iOS 8.1.2 that works on Windows. We are still waiting for a Mac OS X version; however, since a beta of iOS 8.2 has already been seeded and iOS 8.1.3 has already been spotted, we suggest you update to iOS 8.1.2 and jailbreak as soon as possible.