Publish timestamp error - Air 2 Flash CS5

Hello, I use Adobe Flash CS5 Pro to create AIR presentations and when I try to build an AIR application, Flash fails to create the timestamp for the self-signed certificate and shows an error "There was an error connecting to the timestamp server. You might not have a connection to the network, or the server itself may have a problem".

I've tried publishing at home and the server seems to work, so I guess it's something related with the company firewall. Can anyone provide any information about what might be blocking a connection to the timestamp server? Is there some other setting that I can change (other than the JRE proxy settings)?

Thanks a lot,

Michele