This Thursday the 26th, BioWare will take down the Star Wars: The Old Republic servers to perform unscheduled maintenance. During this window, servers will be offline but will return with without the need to download a patch. It is very likely that servers are coming down to address a serious bug discovered by the community.
Quote from BioWareThe servers and SWTOR.com will be down for two hours on Thursday, July 26th, 2012 from 2AM CDT (12AM PDT/3AM EDT/8AM BST/9AM CEST/5PM AEST) until 4AM CDT (2AM PDT/5AM EDT/10AM BST/11AM CEST/7PM AEST). All game servers will be offline during this period. This maintenance is expected to take no more than two hours, but could be extended.
To find out more about this unscheduled maintenance window, head on over to the official post.