i worked this out myself. The issue was the version mismatch.
I was using infinispan 5.1.3 version which had compatibility issues with Weld SE and cdi 1.1. Upgrading the version to 5.2.0.ALPHA2 corrected it, if using infinispan stand-alone.
If using the jboss eap6/jboss as7's in-built infinispan, we need to upgrade the infinispan module from whatever version that's available by default on the installation to the 5.2.0.ALPHA2.