@support: Do you have any suggested values? I increased the time to 60 seconds and the memory from 128 to 256 and my server support people checked my edits and rebooted the server for me.
The same number of pages get indexed by the generator and the displayed page in the browser never forwards to the page usually shown when completed, but I noticed that I saw the page refresh for awhile while the script was running (before nothing else happened with it). I check its completion by examining the timestamp of the generated files in the data folder via FTP.
I tired it on several different browsers with the same results. I haven't tried downgrading back to 6.0 but that may be my next try depending on what you think.
Edit to add: I'm only generating a .gz version of the sitemap, no others. I don't know if this factors in or not.