I agree. This is certainly NOT resolved. I was so frustrated with Firefox 3 and Safari lagging on OS 10.5.4 that I downgraded to 2.5. Now that I’ve done that everything works perfectly again!
2.5.1 was a mess with the auto-save error because no matter how many times I deleted the wp-admin and wp-includes directories and re-uploaded them, the same error occured.
So, obviously, now that 2.5 is working perfectly, the error must be part of 2.5.1 because it works great now.
So those of you who are having trouble with 2.5.1, just downgrade to 2.5 All of my plugins still work swimmingly and now posting is a breeze.
Matt
https://matt-moody.com