The GDAL JasPer (JPEG2000) driver has been changed to be a plugin. And a 'disabled' folder was added for GDAL plugins. While the driver used for writing images is controllable in GDAL programs, reading is not and GDAL uses the first driver it finds. This 'disabled' folder allows some control over which driver is used for reading JP2 images in GDAL (JasPer, MrSID or Kakadu).
And speaking of reading JP2 images, there seems to be a bug with the JasPer driver for reading JP2 (writing has no such problems) - it's excrutiatingly slow. But the MrSID driver reads JP2, slower than JasPer would normally, but faster than it is now. Use the 'disabled' folder to disable JasPer temporarily to force a different driver - MrSID, or Kakadu (none available from me at this time) if one has the Kakadu libraries available to them.