I'm getting the same file writing errors as others have. I'm not sure but it may have been after I installed WordPress 2.5.1. I've tried deleting and reinstalling Google XML Sitemaps, created the two files and uploaded them, changed their access to 777, 755 and 666. Tried the rebuild and then debug link, and still have the problem. Not sure if I FTPing the files to the correct place. I'm using BlueHost and I've tried two different locations as follows:
In both cases the file size remains zero.
Any suggestions would be appreciated.