i am also wondering if it is something with the ethernet shield. i have been able to crash the arduino if i purposfully send lots of information over to it really fast. it just stops responding.
I think the 5100 chip is capable of only four sockets, so if a socket is not properly allowed to close, it may become unavailable for future use.
i am also wondering why my arduino freezes when i have the watchdog enabled. should that not reset the system?
I haven't looked at the watchdog code. Is it a proven design?
i tried to use the "Wstring.cpp" and "Wstring.h" from Paul Stoffregen's teensey system. everything compiled, but it would no longer function and i have not determined what is causing it to not work.
I think those librarys are included in the latest arduino core design. If you use the string functions, under some conditions it is said that used memory is not automatically released, and might eventually deplete available memory, causing a freeze. Recently various patch solutions have been posted