Simple2Ext (S2E) Quick Guide:
Please make sure that you use ROM version v1.4 or later, as it includes a patch to prevent S2E’s aggressive filesystem tweaks that cause corruption.
 

• To make absolutely sure that your /sd-ext partition is not corrupt, manually format the /sd-ext partition:

• Install S2E from Market.
• Open S2E, click the Menu key -> Settings. Enable “Mount as ext4” (mandatory). Do not select “Set read buffer”, as the default value of 2MB will cause extreme lag on our phone. My port already sets the buffer to a more conservative value of 256KB, which I have found works best.
• Close the app and reboot.
• Open S2E again, select the folders you wish to place on the SD card. I recommend that you don’t move the “Download cache” folder, as it makes more sense to leave it in internal storage (/data).
• Changes will take effect on the next reboot. Note: your dalvik cache will be rebuilt, so this reboot will be slower than usual.