Do you have the problem of having the menu/home button pressed on your E-51, and yet the menu is not displaying/froze?
Had search the nokia discussion forums, and tried out the following and none worked for me.
1) Stick to the GSM network and prevent it from switching between 3G and GSM.
2) Reassigined the left shortcut button to anything, except for menu.
Finally, what works for me is that I need to disable the keypad autolock function. By doing that, it's been good so far. It's 5 days and counting. Keeping my fingers crossed now.
Will let you know if it fails too.