For some unknown reason, suddenly I cannot 'show' shetches within one particular part file. Was working on the file, showing and hiding sketches in order to create/edit features like normal, and don't know what might have happened, but can't show sketches now. Still able to show/hidw sketches in every other part file I've opened. Tried closing and re-opening the file, rebuilding the file, renaming the file, closing and re-opening SW, and restarting my computer. Is there a setting somewhere or something, or is this a glitch? Please help. Cannot work on this file until I resolve this issue. Thanks.

Using SW13 SP1.