I use Firefox and never a problem, sounds more of a cookie problem your end. Have you allowed this site to set cookies? :?

No problem on my end. What version of Firefox are you using? To accept cookies: Select Tools Then Options Then Privacy And make sure that "accept cookies from sites" is checked. I hope that helps.

If you instead click the Exceptions button on the far right of that, you can then paste our domain in and click Allow. That way you can still prevent other sites setting cookies. This can also be used to prevent key sites with the Block option, or limit the duration of set cookies with the Allow For Session option. :)