I ran the snapshot yesterday to try out the new chunk loading and graphics improvements. Today I tried to load up my 1.7.10 world using my 1.7.10 profile, and the game crashes after I select a world:

java.lang.IndexOutOfBoundsException
at java.nio.Buffer.checkIndex(Buffer.java:532)
at java.nio.DirectIntBufferU.get(DirectIntBufferU.java:253)
at bma.a(SourceFile:271)
at bma.a(SourceFile:220)
at bao.a(SourceFile:1694)
at bao.a(SourceFile:1652)
at bjb.a(SourceFile:125)
at hd.a(SourceFile:70)
at hd.a(SourceFile:13)
at ej.a(SourceFile:174)
at bao.p(SourceFile:1585)
at bao.ak(SourceFile:774)
at bao.f(SourceFile:728)
at net.minecraft.client.main.Main.main(SourceFile:148)

I used TimeMachine to restore my options.txt file just on a hunch, and now the world will load.