I have the same problem
I was testing youwave the last few days and it was awesome, installed whatsapp all working great, purchased the program got the activation key etc etc
now it cant play sudoku ...... Installation Failed [INSTALL_FAILED_INSUFFICIENT_STORAGE]
its a new install with whatsapp surly that cant be the limit of the program ?
just checked under applications/storage use and 80meg used and 692 free ??