Hello, SEO Ultimate.
I found a bug in permalink tweaker:
My categories slugs contains japanese characters.
Original category links were like this - http://www.site.com/category/main-メイノ/
After permalink tweaker its supposed to be like this - http://www.site.com/main-メイノ/
If I go to this category from wordpress theme (I click on it in categories list, for example), redirect will be ok.
If I try to access this category dirrectly (I tape "www.site.com/main-メイノ/" in the adress bar) or I reload the page, I will get 404 page.
Tested it on clean wordpress installation without themes or plugins. Tried it only with categories URL base removement, maybe it will also work with tags or archives too.
I hope, you will fix it.
Thank you for your attention.