GS724TS - Javascript Errors

AHi all,

I have 3 switches configure in a stack. I've previously had no problems until one day when I tried to log in to manage the device, and navigated to Switching -> VLAN -> Advanced -> VLAN Membership nothing comes up in the actual tagging tagging dialogue.

If you select a new VLAN ID, and look to the browser console the following error trace appears: 

Uncaught TypeError: Cannot read property 'selectNodes' of null
    at theClass.BaseTable.serializeInnerNodes (BaseTable.js:4)
    at theClass.Membership.display (MemberShip.js:407)
    at theClass.Membership.complete_get (MemberShip.js:706)
    at CallBackObject.ReadyStateChange (CoreInfrastructure.js:6)
    at XMLHttpRequest.XmlHttp.onreadystatechange (CoreInfrastructure.js:6)
BaseTable.serializeInnerNodes	@	BaseTable.js:4
Membership.display	@	MemberShip.js:407
Membership.complete_get	@	MemberShip.js:706
CallBackObject.ReadyStateChange	@	CoreInfrastructure.js:6
XmlHttp.onreadystatechange	@	CoreInfrastructure.js:6
XMLHttpRequest.send (async)		
CallBackObject.DoCallBack	@	CoreInfrastructure.js:6
BaseTable.get	@	BaseTable.js:4
GuiObject.superclass	@	CoreInfrastructure.js:4
Membership.get	@	MemberShip.js:141
onchange	@	home.htm:1
ListPicker._handleMouseUp

I reliase I'm using an older model however I really need this to work. I have tried with multiple different browsers and multiple different computers, all produce the same results. 

Thanks