for what it's worth, in every sense, the wallet seems to work.

From the picture you sent, we can note two things:
1) At that time the wallet was still synchronizing block-chain and loading a large number of blocks.
So even generating POS blocks, these could not be sufficiently up to date with the rest of the network,
and I guess that is why they have been rejected by other nodes.

To prevent this from happening, you should start your wallet frequently, so that you synchronize it more often,
making the operation even shorter.

A safer alternative is to lock your wallet before you close it, this inhibits any further activities (including POS).
After starting the program, the synchronization begin, and only when it has been completed successfully,
you can unlock again your wallet for POS.  (Other type of coin disable automatically POS during sync,  but not all)

2) You had a low number of connections to the network.
This greatly increases the chances of creating orphans blocks.
Theoretically, this event is not a big loss, the generation of the POS block should be tried again some time later,
as soon as possible, but if the condition persist or the net is too slow (lag) the orphan block may be repeated again.

However, it may be useful to increase the number of fixed nodes known to the wallet, modifying the list indicated in
summercoin.conf with a more updated list.
I hope someone with many active nodes will publish an updated list.

These are general recommendations gathered here and there in the guides of other coins with the POS,
which are definitely expressed more clearly in their FAQ, and should also be valid for SummerCoin.