Mail srores going offline?

What will cause the mailbox stores to dismount in MS Exchange 2003? This seems to happen everytime there is a restore to database or backup (my own observation). The exchange admin states that the issue was with the data cable perhaps the NIC card. I beleive the issue is with improper Volume Shadow Copy service not properly implemented or non existent.
Could you please clarify the issue? Will loss of connectivity cause the dismount?
Thanks.