I recently started using Nokia's X2-00 handset (it is my sister's handset :-) ) And from the day one I started facing problems with the phone. It used to get hanged now and then. I did a soft reset, followed by hard reset, restore factory setting etc but still no improvement. Then I searched on google and found many articles saying that this is due to the memory card. The memory card Nokia supplied with the phone, is actually not compatible with the phone. I even changed my memory card, but the problem still persisted. After googling a lot, I came to know that, the problem is not with the memory card, but with the software version of the phone. The latest firmware version for Nokia X2-00 is 8.17 and my phone's firmware version was 4.8 (you can check your phone's firmware version by pressing *#0000#) So, I just updated my phone's software to 8.17 using the Nokia Software Updater utility (just google it you will get the link to download it, or if you have Nokia Ovi suite installed then connect your phone, start Ovi suite, go to Tools -> Software updates) and everything was working normal !!!
If most of you are also facing the same problem, then just check the version of the firmware on your phone and update it to 8.17. If it is already 8.17, try reinstalling the version. The update worked for me, hope it works for you as well.
Download Nokia Ovi suite from here