Try resetting data from within Impulse:
-Click the blue menu button in the upper left
-Choose 'Preferences...'
-Click the 'Reset Data' button
-Close impulse and relaunch it. You may notice a long update time, which is normal as it is rebuilding the deleted info.
If this does not resolve the issue, I would suggest uninstalling Impulse, rebooting your PC, and then reinstalling from the latest installer build here:
http://www.impulsedriven.com/impulse_setup_full.exe