I can assure you that using task manager to end task on ImgBurn isn't going to corrupt your OS.
The sync cache command is processed by the drive and ImgBurn simply waits for it to say it has finished. If yours isn't finishing, either your drive got stuck processing it (doesn't like the discs etc) or your drivers are messing with the response.
If the drive is stuck, you'd have to totally power the machine off so it can reset properly. Take the disc out as it powers back up.
If it's the drivers, update them. What controller have you attached the drive to?
Right click the drive selection drop down box and pick family tree. Close the prompt that comes up and then copy + paste everything from the log window please.