I was having trouble depositing into Virwox until about a week ago. Maybe this has something to do with it.
What funding method was that giving you trouble?
If that was a widely used method, yes that method becoming available again could have been a contributor.
One aspect of SLL is that most of its userbase is in Europe. There were likely people wanting to hold BTCs or USDs even with the Greek election uncertainty. That might explain why the price dropped about 10% after the election and that Greece probably won't be exiting the Euro.
The tading volume certainly had risen above normal in the past few weeks: