The fix:

*** htsthread.c.orig    2006-08-05 08:55:46.643764360 +0200
--- htsthread.c 2006-08-05 08:53:13.000000000 +0200
***************
*** 69,75 ****
--- 69,77 ----

  HTSEXT_API void htsthread_init(void ) {
  #if USE_BEGINTHREAD
+ #if (defined(_DEBUG) || defined(DEBUG))
    assertf(process_chain == 0);
+ #endif
    hts_mutexinit(&process_chain_mutex);
  #endif
  }
*** htslib.c.orig       2006-08-05 08:55:54.934959276 +0200
--- htslib.c    2006-08-05 08:52:07.000000000 +0200
***************
*** 5038,5043 ****
--- 5038,5044 ----
    if (!hts_init_ok)
      return 1;
    hts_init_ok = 0;
+   htsthread_uninit();
    return 1;
  }