Independent of how many VMKernel port groups (Management, vMotion, iSCSI, ...) you configure, you can only configure a single gateway address. Assuming the iSCSI storage is on the same subnet (192.168.1.x), you don't need a gateway address for this subnet and you'd usually configure the gateway address for the Management port group. Other than this I don't see a reason why the Management would stop working!? What about the vMotion subnet, how is this configured. Maybe it would help if you'd post a screen shot of the virtual network configuration.
André