Out of curiosity, are you using the latest version of DBI? Some bugs were fixed recently, and maybe the errors you encounter are related? Note that the latest version is in russian. You should get familiar with how the app works in the older english versions before you attempt to navigate through the menus of the russian version. But it's manageable. If that doesn't solve the signature errors, then your nsp/xci files have probably been tempered with before you acquired them.Hi Dust2dust, I thank you too.
I did what you seggest and now games are returned to work!
I still receive signature error when I install from dbi, but they work, as said.