Firefox 11 is disabling Java plugin versions that are below version 1.6 Update 31 or between 1.7.0 and 1.7.2 for Windows computers only. This affects the use of Host On-Demand (HOD), including UIS, due to its Java requirements. A resolution has been found for this issue as of April 9, 2012.
Instructions to re-enable the Java plugin are available here. Only someone with administrative rights can perform this task. Mac OS X computers are not currently affected by this Firefox update.