This looks like the same issue I'm having, however no resolution of it just yet!
Oddly, I only have the issue on one particular website. If I move my xml-sitemap generator to any other website, it doesn't fault. I've even downloaded a copy of the website it runs away on and it still works perfectly OK.
When it works on the offline site, it will generate 463 pages for the sitemap. When it runs away on the live site,it gets to 2000-odd pages and won't stop!
In the front end interface (on the broken site) is this..
Already in progress. Current process state is displayed:
Links depth: 13
Current page: index.php/reviews/index.php/index.php/component/mailto/?tmpl=component&link=aHR0cDovL3d3dy5nZW9yZ2lhbW9mZmV0dC5uZXQvaW5kZXgucGhwL3Jldmlld3MvaW5kZXgucGhwL2luZGV4LnBocC9yZXZpZXdzLzE5Ny1kb2N0b3J3aG8tZGQ%3D
Pages added to sitemap: 1023
Pages scanned: 4300 (29,133.5 KB)
Pages left: 915 (+ 1272 queued for the next depth level)
Time passed: 0:27:05
Time left: 0:05:45
Memory usage: 5,146.5 Kb
Now I know that I don't have 13 levels and I know that there is something wrong with the site, looking at the Current page line, it's indexing: "index.php/reviews/index.php/index.php/component/mailto" and that just isn't right!! I don't use index.php as the pages (as they're SEF'd out), so it's finding url's that don't exist!
Can anyone please point me in the right direction?