Some suggestions to help minimize the occurrence of corrupt fit files on a Forerunner 35
Avoid pressing stop or pause during an activity.
Sync your watch, backup the \GARMIN\ACTIVITY folder, then do a full master reset of your Forerunner 35 using these directions - Restoring All Default Settings.
Perform a weekly cleanup of the \GARMIN\ACTIVITY folder using these directions - Removing Recorded Activities to Free Up Space. The F35 seems to have problems with longer activities, so this step is important before a longer event.
