Solving the Memory card problem in any multimedia phone is really a cumbersome task. I got the same problem in my Nokia 7500 Prism. I would not even think to repair the problem, but I loved that phone very much. That is why I spent a big time on that phone and finally solved the memory card problem. I thought to bring an IC and change it. But then I removed the IC and made the jumper like this. And it worked. So, if your are also getting the same problem then please make jumpers as shown in the picture. Nokia 6300 also has almost the same PCB configuration. So this trick would also work on that phone probably.