Mojang has been released version 1.7.8 with an important bugfix to fix some server crashes, and to resolve some skin related issues (including more crashes).
Because this is important, let me repeat that last sentence:
Please make sure that you are in the correct server mode (online mode/offline mode) when you start the 1.7.8 server for the first time, because profiles are not compatible between these two server modes.
Cross-platform server windows exe:https://s3.amazonaws.com/Minecraft.Download/versions/1.7.8/minecraft_server.1.7.8.exe
Author: Mojang Team