>>>Here it is, Dragan:
>>>http://forums.sygatetech.com/showthread.php?s=8f865b1438fd84b4e62464c974f3d644&threadid=99
>>>
>>>I hope it does solve your problem.
>>
>>I did learn a lot this weekend, fighting this problem, and the above link did provide some interesting insight - thanks for the tip.
>>
>>However, the MTU value was already there. The problem I'm experiencing seems to narrow down to a timeout I'm getting whenever I try to upload anything above 8K or so (which, somehow, looks like only 1K of email).
>>
>>I'll probably have to start a new thread on this, if I don't solve it soon.
>
>
>Sorry about that. As my friend had described it, it sounded much like your problem.

Update - knowing what to look for, I've found it - the document was on my disk all the time:
"RASPPPOE
PPP over Ethernet Protocol
for Windows 2000/XP/2002
written by Robert Schlabbach"

I've actually got it with the disk from my ISP. Funny they had no idea about this - the Earthlink/Sprint combination sounds pretty much like "the hardware guys will blame it on software, and the software guys will blame it on hardware". I talked with both, and they blankly stated that internet connection sharing with DSL is not supported. Buy a hub.

The value of 1462 that the article you mentioned proposes is probably working in most cases, but this Schlabbach's article gives an exact method of determining the MTU:

ping -f -l xxxx Address

Where Address is the name or IP address of the server you have problems accessing. For xxxx, start with 1464 and lower the number until you get a reply. Then add 28 to the highest number at which you get a reply. The result is the Path MTU.

In my case, the magic number was 1460. So yes, you nailed my problem and I'm not getting extra whites in my beard. (why do they call them grays when they are white?)