Uninstalling and re-installing is a last resort method of trying to fix the program.
Without further details, the 2 most likely causes for this issue are:
The program settings have become corrupted and need resetting - File, Settings, Reset program . . . - note this will lose any customisations you have made to the programs settings.
The project settings have become corrupted - in which case you try the following:
With the project open select File, Manage movies, Export - give the export a name - this will create a file with the .MVD file extension.
Start a new project and select File, Manage movies, Attach - browse to the MVD file you saved above and load/attach it.
Save the new project - the timeline cursor should now work.
Try a Windows "Restart" This has a different effect to "Shutdown" then "Start" and has helped where a similar problem to yours has occurred as a result of some Windows update not installing properly.