Yesterday Sony released firmware update 1.65 for the PS Vita... and then quickly yanked it offline. Apparently the 1.65 has some serious issues - namely problems with adhoc multiplayer. To deal with the issues caused by 1.65 and to add some new tweaks to the handheld, Sony has released firmware update 1.66. The 97MB update fixes the issue with adhoc wireless multiplayer on PSP games and adds an assortment of usability tweaks.
Chances are it also deals with some strange hacks related to some PSP games (which were pulled from the PSN store last week) that allowed users to play homebrew content on the platform. We have not confirmed whether the update deals with that problem or if Sony is still working on it..
Source: Vox Games