To reproduce (at least on my Fedora 17 laptop), start 0.8.2rc2 run getblocktemplate a few times, call stop.
Here is the outcome in valgrind: ==17973== Thread 1: ==17973== Invalid read of size 4 ==17973== at 0x3BD3209B20: pthread_mutex_lock (pthread_mutex_lock.c:51) ==17973== by 0x4201E6: boost::recursive_mutex::lock() (pthread_mutex_scoped_lock.hpp:26) ==17973== by 0x423595: boost::unique_lock<AnnotatedMixinboost::recursive_mutex >::lock() (sync.h:22) ==17973== by 0x571047: CWallet::ReturnKey(long long) (sync.h:70) ==17973== by 0x571109: CReserveKey::ReturnKey() (wallet.cpp:1814) ==17973== by 0x4A2AB5: CReserveKey::~CReserveKey() (wallet.h:332) ==17973== by 0x3BD2638B80: run_exit_handlers (exit.c:78) ==17973== by 0x3BD2638C04: exit (exit.c:100) ==17973== by 0x3BD262173B: (below main) (libc-start.c:258) ==17973== Address 0x191b3d40 is 352 bytes inside a block of size 840 free'd ==17973== at 0x4A0736C: operator delete(void_) (vg_replace_malloc.c:480) ==17973== by 0x44AD0D: Shutdown() (init.cpp:115) ==17973== by 0x4560E0: AppInit(int, char) (init.cpp:241) ==17973== by 0x418F39: main (init.cpp:254) ==17973== ==17973== Invalid read of size 4 ==17973== at 0x3BD32057A6: __pthread_mutex_lock_full (pthread_mutex_lock.c:145) ==17973== by 0x4201E6: boost::recursive_mutex::lock() (pthread_mutex_scoped_lock.hpp:26) ==17973== by 0x423595: boost::unique_lock<AnnotatedMixinboost::recursive_mutex >::lock() (sync.h:22) ==17973== by 0x571047: CWallet::ReturnKey(long long) (sync.h:70) ==17973== by 0x571109: CReserveKey::ReturnKey() (wallet.cpp:1814) ==17973== by 0x4A2AB5: CReserveKey::~CReserveKey() (wallet.h:332) ==17973== by 0x3BD2638B80: __run_exit_handlers (exit.c:78) ==17973== by 0x3BD2638C04: exit (exit.c:100) ==17973== by 0x3BD262173B: (below main) (libc-start.c:258) ==17973== Address 0x191b3d40 is 352 bytes inside a block of size 840 free'd ==17973== at 0x4A0736C: operator delete(void_) (vg_replace_malloc.c:480) ==17973== by 0x44AD0D: Shutdown() (init.cpp:115) ==17973== by 0x4560E0: AppInit(int, char*) (init.cpp:241) ==17973== by 0x418F39: main (init.cpp:254) ==17973== bitcoind: /usr/include/boost/thread/pthread/pthread_mutex_scoped_lock.hpp:26: boost::pthread::pthread_mutex_scoped_lock::pthread_mutex_scoped_lock(pthread_mutex_t): Assertion `!pthread_mutex_lock(m)' failed. ==17973==