N2024 dual Vlan Switch config

Hi All, 

I have a N2024 series switch,  - firmware version below

ee-dr-sw1#show version

Machine Description............... Dell Networking Switch

System Model ID................... N2024

Machine Type...................... Dell Networking N2024

Serial Number..................... CN0P8K2V2829857P0085A03

Manufacturer...................... 0xbc00

Burned In MAC Address............. F8B1.568B.5B4E

System Object ID.................. 1.3.6.1.4.1.674.10895.3053

SOC Version....................... BCM56342_A0

HW Version........................ 5

CPLD Version...................... 13

unit active      backup      current-active next-active

---- ----------- ----------- -------------- --------------

1    6.2.0.5     6.2.0.5     6.2.0.5        6.2.0.5

I currently have it configured for management on an IP on vlan 1, on our lab/office network.

What I would like to do is configure it so that I can access it from vlan 40, from within one of the guests within that vlan 40  - 172.29.33.0. 

I've configured a second management address on vlan 40 on the switch in accordance with this link : http://www.dell.com/Support/Article/us/en/19/HOW10399

However when i try and change the default gw to that of 172.29.33.1, it tels me, that I cant config the gw until i've got an interface belonging to teh same subnet as the config'd gw.

ee-dr-sw1#conf

ee-dr-sw1(config)#interface vlan 40

ee-dr-sw1(config-if-vlan40)#ip address 172.29.33.10 255.255.255.0

ee-dr-sw1(config-if-vlan40)#exit         

ee-dr-sw1(config)#ip default-gateway 172.29.33.1

Warning! Notice! The configured default gateway will not take effect until an interface belonging to the same subnet as the configured Gateway is created and activated.

I'm not really sure how to fix this or what i'm supposed to do.. I'm a bit of a newb on the N /Dell series.

Any help is gratefully apprecated.