creation of snapshot fail somtimes w/ "Cannot allocate memory"

Hello,

I've a daily snapshot that cron umount, delete, recreate and mount every night. sometimes (about once a week) I'm getting the following output:

Logical volume "daily" successfully removed device-mapper ioctl cmd 9 failed: Cannot allocate memory Couldn't load device 'ext-daily'.
Problem reactivating origin part1
mount: special device /dev/ext/daily does not exist

mean that the umount and delete worked but the recreation and therefor the mount failed... how could this be debugged ? any idea what could be the problem ?

thanks,

--Yedidia