PPPoEs Users and Mangle Rules removed

I’m using several routers to administrate clients on my network, and I’ve just next situation:
The same issue happened in two routers. The first one using RouterOS v5.12 ppc, and second router using RouterOS v6.0rc9 x86.
I’m using in both cases PPPoE to authenticate and mangle rules to mark packet and shape traffic with queue tree, and suddenly today in the morning I’ve found that in both routers were removed all PPPoE users and Mangle Rules. I’ve checked the log, and no information about this.
Can anybody tell me what’s happening? Any Idea? Can the RouterOS be attacked by some virus?

I appreciate any information you can give about this.