"The recommended load-balancing method for Catalyst switches is src-dest-ip (CLI command: port-channel load-balance src_dest_ip)."
With 6500's running in pfc3 mode, the channel load balance method is 'src-dst-ip enhanced' or 'src-dst-ip vlan included' by default, which will often cause packet forwarding problems with Wism controllers (referenced in the link above).
6500's pfc mode can be verified with this command:
6500#show platform hardware pfc mode
PFC operating mode : PFC3A
The ability to revert to 'src-dst-ip' only was not originally in 6500 code.
This was added as an enhancement in 12.2(33)SXI3 as documented in the following enhancement bug: