did you move wallet.dat to another wallet (fresh install)?
No I didn't, is that something I should be doing?
PM'd you this (for transparency and to help others);
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what has occurred is that your coins have hit an orphan block.
Mine did the same thing this morning.
here's what I did trying to fix it.
I initially moved wallet.dat to another wallet and found the stake portion of my balance was no longer there.
(I had 4.2sync initially with 1sync in stake)
so the new wallet only showed 3.2sync.
I then moved the wallet.dat back to the original wallet, but deleted all files from roaming/sync except wallet.dat and Sync.conf
resynchronised the wallet and it stuck at block 8200.
restarted wallet from 8200 and it synced up correctly, taking the staked coins back to spendable.
here is the reason that orphan blocks occur, as shown in your wallet minted coins;
When you generated this block, it was broadcast to the network to be added to the block chain.
If it fails to get into the chain, its state will change to "not accepted" and it won't be spendable. This
may occasionally happen if another node generates a block within a few seconds of yours.
however. when the wallet finds an orphan block (the greyed out part) it shouldn't go out of sync.
I hope this issue is fixed by the dev team with wallet v 2.
hope this helps.