catching non-std exception

On FC4 with g++ using STL and Posix threads
and sockets I am catching an exception that
is not a std::exception.  Any idea what it
might be?  An outline of my catch macro is
below.

Thanks,
Mike.

#define MY_MACRO \
   catch (MyExceptions& e) \
   { \
       ...  \\ process them \
   } \
   catch (std::exception& e) \
   { \
       ...  \\ process them \
   } \
   catch (...) \
   { \
       ...  \\ what is this \
   }
--
Michael D. Berger
m.d.berger@xxxxxxxx