I pulled your checkpoints into the source tree and that's what my current QT and linux wallet are running with.  I had a hiccup with the seeder that reset my peercache and so my  two wallets and most likely some others out there were having a hard time staying connected.  I'll know more with the other updates and once I clean out some more loose ends in the QT portion of the wallet.

I also am going to need to get some testers out there with the new QT wallet once I get a beta online.  So far, compiled with QT-5.2.1 and Boost 1.55 (mingw64-4.8-GCC) it is stable but I'm noticing some network quirks that might be related to an LTC issue they were having as well.  More on that when I pinpoint the issue