Getting ths error when starting eMule Plus :
Incorrect versionnumber in server.met (0x3C)

Any idea of what that is?! ..

I suspect, you use some server.met automatic update and sometimes it saves HTML stream (some error) to server.met file instead of the actual data.
0x3C is "<" character which is opening tag for HTML.

What happens when it hits this issue? Is previous server list preserved or is it lost?

nope server list is updated manually ... and the previous server list is lost when this error pops up. At the same time it gives me LowID

You can try to use server_met.old to recover when this happens. Send me your server.met when it happens (compressed over PM). Get the file right after it happens on startup, as it can overwrite it later with empty list.