I am sure this getting lost in translation, but are you saying you reboot the system and it doesn't see the cards installed, then you reboot it again and it sees the cards properly?
My first thought would be to upgrade the system to current software... This will require an active Software Assurance agreement with Mitel. This will be the first step Mitel tech support would tell you to do.
The next thing here would be to ask if all cards that does this, like the system doesn't see any card plugged into the backplane until you reboot? This could be a main control card issue, a power supply issue, or (less likely) a backplane (cabinet) issue. It is also possible one card is causing the rest not to initialize properly on a cold start.
If this only does this on a "cold" start and can be replicated, remove all but one card from the system temporarily and boot... If that works, repeat adding one card at a time until the issue recurs, than the last you card you inserted is likely the culprit.
Basically, in this case it's basic troubleshooting... Find a way to replicate the problem, then eliminate everything you can until you are down to a minimal number of pieces or one thing and replace it and try again until the issue no longer occurs.