Just updated to OS X 10.11.3 (15D21) and every time I launch BaseCamp with my alpha plugged in it crashes.
Ok, I'll bite, what's an Alpha and why is it necessary to have it plugged in when you start Basecamp?
Have you reported the error? Please do if you haven't. Also, could you search for 'Crashed::' in the report and post here the stack trace for the faulty thread in order for me to find your crash report? eg:
Thread 0 Crashed:: Dispatch queue: com.apple.main-thread
0 com.garmin.BaseCamp 0x00bd8e7a map::SubselectionPolyline(gdb::Track_t const&, gdb::Track_t::const_iterator const&, gdb::Track_t::const_iterator const&, glo::Optional_t<double> const&, glo::Optional_t<double> const&, std::__1::vector<geo::Polyline_t, std::__1::allocator<geo::Polyline_t> >&) + 261
1 com.garmin.BaseCamp 0x00b862b2 map::GdbRenderer_t::RenderTrackSubselection(gdb::Track_t const&, gdb::Track_t::const_iterator const&, gdb::Track_t::const_iterator const&, glo::Optional_t<double> const&, glo::Optional_t<double> const&) + 76
2 com.garmin.BaseCamp 0x00b82b39 map::GdbDisplayLayer_t::RenderSubselections() + 919
3 com.garmin.BaseCamp 0x00b81643 map::GdbDisplayLayer_t::RenderRoutesAndTracks() + 1593
4 com.garmin.BaseCamp 0x00b80c46 map::GdbDisplayLayer_t::RenderLayer() + 24