Mgmt vlan is like other vlans. If you want to have redundancy for it, run HSRP and point all devices in that vlan to the HSRP address as default gateway. To fix your problem with pinging the HSRP address, we will need more info. It's worth to open case with Cisco. These are just few things which you might check:
- check the config on both HSRP nodes
- check the "sh standby" for that group if everything is running ok
- check that HSRP MAC address is correctly programmed on switches (CAM table)
- if you have redundant sup engines in one chassis, check that both configs are the same (unless you run native or SRM)
- try with latest versions