Hello, I've been trying several times recently in adding funds to my steam account so I am able to purchase 3500 CE, but steam gives me an error message stating that my CC is unable to be used at that time. I do not believe that it is my credit card, because I have been successful in purchases on other sites but only on steam is where I am unable to purchase anything.
Any kind of assistance would be much appreciated, thanks.
That's a problem on Steam's side, it's quite useless to ask for help here in Spiral Knights' forums.
Try in Steam's forums here: http://forums.steampowered.com/forums/forumdisplay.php?f=17