I also have this problem with the nightly build of JBoss 7.2.0-Alpha1-SNAPSHOT of the last Saturday.
I have a method with a single parameter of type byte []. When the byte array is 10 Kb then the call works fine. When the byte array is 100 Kb then JBoss hangs.
I have used previous versions of JBoss 3,4 uploading and downloading large amounts of data without any problem or limit.