How to change the language in Twenty Eleven *Need help ASAP*

What are the names of your .MO/.PO files?

Hi!
sv_SE.mo
sv_SE.po
thx!

And what is the exact line that you added to wp-config.php?

define ('WPLANG','sv_SE');

All of that looks exactly right.

Next question: where did you get the .MO/.PO files? Are they Theme translation files, or core translation files?

I got it from the Swedish wordpress website, https://wp-support.se/filer/?dl_cat=1 and i got the file “WordPress 3.3.2 ?vers?ttning/translation”

I got it from the Swedish wordpress website, https://wp-support.se/filer/?dl_cat=1 and i got the file “WordPress 3.3.2 ?vers?ttning/translation”

That sounds like your problem, then: those are probably the translation files for WordPress core, not for the Twenty Eleven Theme. Theme translation files are entirely separate – and are placed in separate locations – from WordPress core translation files.