Here is an idea, do not click on the View Sitemap tab.
Then when you run a crawl, the Crawling page will not display the sitemap in a slide window. Displaying sitemaps consumes a lot of memory. When the crawl is finished, then you can View Sitemap.
If you get the Memory Exhausted message when you view sitemap, then refer to my earlier post on how to display the sitemap in smaller chunks.