If it's any consolation...I recently reformatted and reinstalled Windows XP Home on my machine, and am just now getting around to putting my MAME stuff back on the machine. From a clean install of the latest version of ClrMame, I am also experiencing the same problem. My wwwdata.ini file is a 0-byte file. I downloaded the datafiles separately and installed them in the "datfiles" directory, then tried again to use www mode, and got the same problem.

> I have the same troubles as well... started like a week ago. Have tried all
> posted suggestions, no luck so far! :|
>
> //CGA
>
> >
> > > Hmm...weird. It could be possible that some ISP's proxy cache holds an
> invalid
> > > mamedats.zip....so this should get fixed within some time by itself.
> >
> > > It may happen that the automatic transfer mode has chosen 'text' instead of
> > > 'binary' for the download and so the zip would be corrupt and the error
> > appears.
> >
> > > I put an unzipped version of the xml online, try to use
> > > "http://www.clrmame.com/clrmame.xml" for the url string. I've also
> reuploaded
> > > the zip...maybe it works now ;)
> >
> > Tried to use the URL for the unzipped version same problem as before.
> > I can download both the zipped and unzipped version by entering the URL in the
> > browser without any problems. The XML in the zip file has today's date. So I
> > would think that it is probably not a caching problem on the ISP's side.
> > I really don't understand it.
> >
>