Guest,
Hmmm, I just used that same Yahoo web-based mail interface, and noticed no differences....... (9:20pm [PST], Monday 12/03/07)
I do note, however, that on occasion Yahoo will, in it's infinite wisdom, decide that you want to try the so-called beta product, what I think is yet another version of the samo-samo web-based mail interface. I can't speak as to what that entails, I merely turn it off whenever that happens, and I'm right back where I wanna be, using what you correctly term the classical interface.
Options open to you:
A) Swallow your ire, and disable Proxo for the moment;
B) Use a friend's computer; or
C) Go to the library and use a public machine.....
Log into Yahoo (if the library will let you!), then change your Preferences back from beta to standard. That should cure your ills.
Also, note that for some strange reason, the same thing does not happen at the same time to all Yahoo users. The rollout is gradual, and what you're seeing now, that may happen to me tomorrow, or next week, or......

Like I said, they do this as "job justification", and nothing else. If Yahoo really had a clue about what the user wants (and it sure ain't that so-called "enhanced user experience"!!!), they'd fire every programmer they've got, and keep the money. In about a month, they'd be so rich they could afford to cut all fees in half.
HTH
Oddysey