This patch (thanks to Frank Sweetser) should fix the timeout problem
users are experiencing with MySQL versions greater than 5.0.13.  
It can be applied to Bacula version 1.38.7 (and possibly 1.38.5 and 1.38.6)
with:

  cd <bacula-source>
  patch -p0 <1.38.7-mysql.patch
  make
  make install

Index: src/cats/mysql.c
===================================================================
RCS file: /cvsroot/bacula/bacula/src/cats/mysql.c,v
retrieving revision 1.37.2.2
diff -u -r1.37.2.2 mysql.c
--- src/cats/mysql.c	4 Mar 2006 11:10:17 -0000	1.37.2.2
+++ src/cats/mysql.c	7 Apr 2006 14:10:23 -0000
@@ -132,7 +132,6 @@
    mysql_server_init(0, NULL, NULL);
 #endif
    mysql_init(&(mdb->mysql));
-   mdb->mysql.reconnect = 1;             /* so connection does not timeout */
    Dmsg0(50, "mysql_init done\n");
    /* If connection fails, try at 5 sec intervals for 30 seconds. */
    for (int retry=0; retry < 6; retry++) {
@@ -153,6 +152,7 @@
       bmicrosleep(5,0);
    }
 
+   mdb->mysql.reconnect = 1;             /* so connection does not timeout */
    Dmsg0(50, "mysql_real_connect done\n");
    Dmsg3(50, "db_user=%s db_name=%s db_password=%s\n", mdb->db_user, mdb->db_name,
             mdb->db_password==NULL?"(NULL)":mdb->db_password);