I tested it with Firefox, IE, Chrome, two smartphones (T-Mobile), and two different tablets with no problems.
Try logging out and logging back in and clearing browser cache.
I think I recall this coming up in the past with other VBulletin sites, and the problem turned out to be ISP's, or in your case- carrier, using proxy servers to cache web pages in order to reduce bandwidth.
Which probably doesn't help you a bit.