I already posted a new thread, but I am having the exact issue in P3DV4.5 as well.
If you have this exact issue, you shouldn't have posted a new thread. I removed it so, unless your issue is different, don't open a new thread when a new one discussing exactly the same issue is already opened and you even posted on it.
As discussed in this thread, we isolated the problem although we haven't been able to replicate it yet, I could only see it on an user's system via remote assistance. For those affected, it results in the inability to make a "normal" Restart IF the airport cache has already been built from a previous session
If the cache is rebuilt, Restart seems to work ( or, at least, it worked with no issues on that user system I had a chance to try ) so, as TEMPORARY fix, we released a small update that for the time being will always trigger a cache rebuild.
This, depending on your system speed and the number of sceneries you have installed, will like result in a slower Restart. To speed it up as best as possible, I suggest adding all folders you have sceneries installed to the Antivirus Exclusions, which will bring down the cache regeneration time quite a bit. Again, this is just a temporary solution that should help you get going while we find what's causing this.