1. Do the menu command View > View Options and set Compact Cell Extras or Expanded Cell Extras to show Capture Date/Time next to thumbnails in Grid view.
2. Look at the dates under the thumbnails carefully -- are the dates from both cameras the same, or are the years or am/pm different?
3. If the dates look the same, make sure the toolbar is showing at the bottom of Grid view by doing View > Show Toolbar, and post here a full-resolution screenshot of Grid view. That could give clues as to what's going wrong.