With Debian Lenny being promoted to Stable, people may well be noticing an alarming number of available upgrades if they are still using Mepis 7. To solve this issue and prevent potentially breaking your system start up Synaptic, go into settings and amend the list of repositories to specify etch or oldstable instead of stable.

It's probably worth Mepis 8 users checking their settings too and ensuring they're happy with what their sources list is pointing to.