Loading delay?

[Kris@modmynav]

Hello,

I was using copied 2007.1 US map from last year without any problems,
however, recently I've noticed there is loading delay saying "Please wait.."
sometimes it goes nav screen, but sometimes it gets error messages saying "Incorrect DVD/CD" or something similar.
I thought my copied DVD was bad, so I replaced with my stock DVD which is 2004 ver.
It turned up right away at the first time, but today I see "Please wait.." message again.
it doesn't take that long until load map screen but it's bugging me.
I've searched and found hot weather issue? I'm in California and it's pretty hot in here nowdays.
But I've had my X5 since 05', never had this problem at all during past summers.
What's wrong with my Nav system? my MK IV is going bad?
anyone had this problem?

Thank you