Also seen here (OS X 10.9.1 Java 1.6.0_65), just as submitter described. More disturbing than the displacement of 2-block-wide paintings was their removal from the walls (and, if not replaced quickly enough, complete disappearance). Also noted was the following server message:
[19:12:32] [Server thread/ERROR]: Wrong location! (23, 11) should be (23, 12), sx['Painting'/157, l='world', x=379.94, y=80.50, z=191.50]
java.lang.Exception: Stack trace
at java.lang.Thread.dumpStack(Thread.java:1266)
at aqz.a(SourceFile:647)
at arn.a(SourceFile:294)
at arn.a(SourceFile:81)
at arn.a(SourceFile:69)
at nl.f(SourceFile:129)
at nl.c(SourceFile:80)
at net.minecraft.server.MinecraftServer.h(SourceFile:257)
at net.minecraft.server.MinecraftServer.a(SourceFile:228)
at mm.f(SourceFile:182)
at net.minecraft.server.MinecraftServer.run(SourceFile:347)
at mc.run(SourceFile:647)Confirmed; client crashed as Iron Golem approached. Traceback was identical to the one posted. Samuel's work-around (thanks!) allowed me to continue in the same world.
The "dup" bug MC-62140 does not mention that the bug affects updates from the 1.7 release. It only refers to incompatibility between snapshots.