Can you please check the patch version from the about page? Thanks. We know this as a bug in patch 3025 and fixed it in the next patch. You can try to restart Nav it should work fine after restarting. BTW You are expected to get the new patch bundle build soon.
Can you please try to open regedit and rename HKEY_CURRENT_USER\Software\Quest Software\SQL Navigator 7.0.0 to SQL Navigator 7.0.0_bak? restart sql navigator
and try to connect again to see if you can still see the errors.