Resolve sitemap issue with wordpress blog

We have a wordpress blog that despite editing the file permissions, the sitemap.xml doesn't seem to be updating. We have removed the previous sitemap and attempted to build a new one using XML sitemap generator but it seems to time out each time we do this and this also happened when we tried simple google sitemap plugin. When we looked at the old sitemap file, it seems to be referring to a plugin that hasn't been used for several months - karelliev's sitemap which was buggy.

We basically need someone to put a working sitemap on our wordpress blog