[galaxy-user] bed to bigbed conversion

Dear users, I am only recently beginning to discover Galaxy, so please bear with me... I am trying to convert a bed to bigbed file, but the job remains 'grey', it does not start. I repeated the same conversion with the UCSC sample file (http://genome.ucsc.edu/goldenPath/help/examples/bedExample.txt) , but it still does not work. I simply uploaded the file directly from the link and then used the bed-to-bigbed conversion tool. So either I am doing something wrong or could there be an issue with this conversion on the server? Thanks for your insights, Gijs