Check your "stake". Supposedly your coins turn into "stake" when used to create stake blocks, then turn back into balance 30 days or whatever later.
Any you do not want used as stake you can set a hold back value of how much to not use as stake and thus to keep as balance.
-MarkM-
Actually the coins become available again once the block is confirmed 520 times, the same as the POW blocks and the coins generated in the POS block.
30 days is the amount of time a coin(s) need to sit unspent in order to be eligible to create a POS block.
Added: Basically the "Missing" coins were converted to "stake". If you do a command line ppcoind getinfo , you will see the coins under stake. Once the block they created matures (520 confirms) the coins in stake used to generate the block return to balance + the block reward will be put into your balance.
Example : Transaction ID: 008aaadf12ec6abb379b71c7c0077fe749c6c18dfae3aade37b2c4ed48bc16a3
http://www.ppcexplore.org:2750/tx/008aaadf12ec6abb379b71c7c0077fe749c6c18dfae3aade37b2c4ed48bc16a3You mined proof of stake block 7768
http://www.ppcexplore.org:2750/block/8652fd35b43ce21007c9c04d927930a5fccc84b2a9daf00b7b456c95f82f2dbdWhen that block matures you will receive the 1360 PPC generated,
and the coins used to generate that block (in stake) will also be returned to balance. Corrected by TheSeven. POS reward is 1%.