Missing slash in sitemap /%post_tag%/ instead of tag name

Hello,

I have been trying to solve this myself, but with just a couple o months of experience in WP my ideas are limited. Since updating from 3.0.5 to 3.1 I noticed on all of my WP sites (six total) that after creating a sitemap (no matter which app I use) there is a slash “/” missing just after the domain extension (in my case .pl) and just before the custom category/tag alias. Another thing is that instead of showing a tag name in sitemap URLs, only /%post_tag%/ appears.
My current configuration on most of the sites is: pl_PL, custom Artisteer Theme (I have switched the language pack with the one from a TwentyTen theme), plugins: all-in-one-seo-pack, auto-tag, breadcrumb-navxt, scaleable-contact-form, simple-captcha, strictly-google-sitemap, strictly-tweetbot, tdo-mini-forms, wordbooker, wp-pagenavi, wp-print.

I have done some tests and the results are as follows. I installed a clean version of EN WP 3.1 and only added strictly-google-sitemap plugin. With custom structure Permalink the sitemap generates with the error described above. The same with Day and Name, Month and Name, Numeric setting. Even when I delete aliases from category and tag, still the slash and tags are missing in the sitemap. Without aliases it shows: for categories<loc>https://www.anonse.lublin.pltag/%post_tag%/</loc> and for tags <loc>https://www.anonse.lublin.plcategory/uslugi-szewskie/</loc>

The only working configuration is with Permalink set to Default, then all sites index just fine in my sitemap.

You can find my sitemap screenshot here.

To compare I installed the WP 3.0.5 and … the problem is gone?

Any idea? How to fix this to continue using 3.0.5 with custom Permalink?

Thank you for any help.

Sevi