Error taking snapshot 0x70021 with unknown error 0x590001

Hi,
trying to backup a partition with Acronis True Image Echo Server for Linux (build #8398) the software returns to me the error 0x70021 with error 0x590001.

On my Linux system (RH EL 5.3) I have three partitions: only one of them causes the error (partition hda4).

With the previous version (#8206) I had a similar issue that solved "by itself" (meaning that I had no more errors after a reboot).

I've upgraded to the last version (and rebooted) but with no luck.

On the partition I have a DB but, nighttime (when I keep the backups), it has no access.

I've already upgraded snapapi drivers (26-0.7.45-2).

Please let me know how to solve this issue (and sorry for my bad english).

Regards,
Nadir