The only two things you can do to/for a digital camera is change batteries and change memory card.
If your rechargeable batteries have been in use for a long time, they may be dying. You could try new rechargeable batteries.
Your camera uses Smart Media which was never particularly fast. It too could be dying. Try a new memory card.
If you are shooting in TIFF format, that could explain the lengthened time between shots.
That is about all of your options.
I have noticed that my camera (Camedia C-4040z)takes longer and longer to transition from one photo to the next... ie.. I am often missing getting a second shot of something as it is still 'writing' it to the media card. Sometimes formatting the card or fresh batteries seems to help but other times it doesn't.. Is this a common problem and is there a 'cure'? Any helpful hints appreciated! Thanks!