> A longer term fix would be to map the long url into
> a shorter path name, similar to as is currently done
> for dynamically generated files, however I expect
> there is a lot of work to do that.

If the options -> Build -> Local Structure Type is anything other than site
structure, it does exactly that (indexFFFF.html)
There is also DOS names and ISO9660 names options.

Try changing LST or DOS. If you get the same error, then it's not a problem on
disk, it's a problem with the zip cache code.