/sd-ext gets suddenly remounted read only during work
Remounting as read-only is an action taken by Linux-based operating systems (including Android) in case of errors accessing the filesystem. In this case it probably indicates that your micro-SD has been (partially) corrupted. There are several possible causes of corruption like this:


Using the phone as a USB mass storage device and unplugging it while a write is in progress
The phone rebooting while an app or the OS is writing to the filesystem
A bug in the ext3 driver in the ROM you're using
A physical error on the SD card due to excessive heat or cold, mechanical shock, manufacturing defects, strong magnetic fields, &amp;c.


Whatever the root cause, try plugging your card into a card reader on a PC and checking it for filesystem errors (for example, using fsck on a GNU/Linux box).