Error 400 when visiting website on Firefox

[WindLing]

I get this error when trying to visit any Daz 3D webpage (main page, forum, shop, etc) in Firefox, since around 2-3 days ago:

Error 400 Bad Request

Bad Request
Guru Meditation:

XID: 1732335958
Varnish cache server

However I can visit the website normally in Internet Explorer. I don't use IE though, does anyone know why I'm getting this error?
My Firefox is up to date, with only the necessary plugins like Java, Quicktime, iTunes App detector, Adobe Acrobat, Shockwave, Flash, Silverlight, and Windows Media Player.

 

[dale]

This is an odd one... I have not seen this one for the longest time. I trust you have tried cleaning cache, cookies, etc.?

 

[J03]

I thin clearing your cookies will sort this one out - I've experience similar problems in the past.