Turn your camera off, remove your batteries for about 30 seconds and let it reset to default. Then try inserting the batteries and see if this helps. a link to go to is: www.olympus.com, then select americas, then select support, then select your camera, then download your manual in PDF format.
there is firmware built-in software which the camera uses to work properly. As a software, you can update it by connecting the camera to a PC and running the Olympus Master software that should have been included with the camera.
Then Set (PC MODE) in the E-300's (Set up Menu) to (Storage). If the operating system is Windows XP, remove the memory card before connecting the E-300 to the PC.
In the Olympus Master software Help Menu, you can look for "update firmware" to follow the instructions. Good luck
But be forewarned that it will only work if you have the newest Olympus Master Software Update, Olympus Master 2. Olympus Master 1.1 will not be able to connect with the online server. Luckily, Olympus Master 2 is a quick and free download from the Olympus site.
Otherwise this could be an intermittent shutter problem or speed setting going astray?
Look like it may be a trip to the Olympus Repair shop
Try to set all menu items to default as much as you can. Some cameras have a reset to default setting or a button to reset to default.
After setting to default, try the camera again.
If all fails, this camera will need repairs.
If it is too old, and not worth it, it may be the best to sell for parts on a site such as Ebay.