might be good to find out what part of the change is causing the problem.  Upgrades to 1.6 were to help with memory leak problems with other skins and IE.  reversion could be done specifically for nokia770 but this probably means both prototype and scriptaculous as these are usually tied together rather tightly.

I used a diff tool to compare 1.5.1.1 vs 1.6.0 and then tried reverting different sections of the 1.6.0 prototype.js to the 1.5.1.1 content.  I wouldn't even term my attempts as "educated guesses"...more perhaps along the lines of "random wishful thinking."  And my attempts were to no avail.  This is WAY over my level of expertize.

I will point out that most of the chatter at http://www.prototypejs.org/2007/11/7/prototype-1-6-0-script-aculo-us-1-8-0-and-the-bungee-book-now-available
seems to be clustering around two issues:

The fact that the hash implementations have changed: http://www.prototypejs.org/2007/11/7/prototype-1-6-0-script-aculo-us-1-8-0-and-the-bungee-book-now-available#comment-17964

And the fact that custom events now need to be namespaced: http://www.prototypejs.org/2007/11/7/prototype-1-6-0-script-aculo-us-1-8-0-and-the-bungee-book-now-available#comment-17996

...not that I really understand the implications of either of those issues for the Nokia770 skin, so I apologize in advance if those are red herrings. 

I did just try running javascript-lint from http://www.javascriptlint.com/download.htm against prototype.js 1.6.0.  Lint returned 190 warnings, ranging from 

 lint warning: missing semicolon

to 

 warning: test for equality (==) mistyped as assignment (=)?

I'm totally not sure if any of these are serious, though.

change 15354 reverts to 1.5.1.1 of prototype.  A quick test revealed that scriptaculous doesn't mind the older version in this case, so I left that alone.  It's worth testing to be sure this all works, and also IE so that we make sure the memory leaks aren't brought back due to 1.5.1.1

My quick test of SVN 15463 seems to show that the immediate recent problems with the 770 skin on the Nokia 770 browser are solved.  I'm not much of an IE user, but, hopefully, other folks will squawk if reverting to 1.5.1.1 of prototype.js introduces other problems with that browser.

Sounds like this is fixed.  Please reopen if it's still an issue.

only todo was to verify that the memory leak didn't return on IE7.  I didn't get a chance before going away, and can't do it until I'm back at home Jan 1 or later.