Thanks for presenting your solution!
I have noticed that
http://bchain.info/SLM has stalled. I have written the site owners, perhaps they can restart the daemon, so we have a working block explorer again. Actual block height should be above 562700. Slimcoin.club, unfortunately, has not returned, but the domain still is registered until July 2016.
Note: when I type "slimcoind getpeerinfo" I get some peers stalled around block height 555000 (particularly 555099 and 555106).
I run the block explorer bchain.info, and the client I used for slim was outdated. Just updated to a new version, once its synced the explorer will be working again.