Unsupported file format?

Hello,

i got this error on google webmaster tools

Code:

Unsupported file format 
Your Sitemap does not appear to be in a supported format. Please ensure it meets our Sitemap guidelines and resubmit.

i reinstalled the Download vBSEO Sitemap Generator v1.7 again

but i got the same result
even after resubmitted

Code:

Unsupported file format 
Your Sitemap does not appear to be in a supported format. Please ensure it meets our Sitemap guidelines and resubmit.

By the way

this was working fine 2 weeks ago

Regards

Hello,

make sure that you have 0666 permissions for vbseo_sitemap/data/downloads.dat file and resubmit sitemap.