Hey Musher. You're thinking of Lassa which they sold in Aug 2014 to Kineta Four as part of the "Optimization" program.
As far as Dengue goes, they had a 5 year development grant from NIH which ended in May but was extended to April 2017. In the last 10k Siga says "We are seeking partners for our Dengue Antiviral drug candidate to support further development activity."
The same document makes no mention of the broad spectrum antiviral but it is still listed on their website under research and discovery.