[intelliot]

Yes, I have uploaded all of the files and they are all the new versions, overwriting the old files... I am using SmartFTP.

The upgrader found some old or outdated language files.

Please make certain you uploaded the new versions of all the files included in the package, even the theme and language files for the default theme.

[[Unknown]]

Are you using any languages other than English?

Have you tried uploading just the Themes/default/languages directory?

-[Unknown]

[guytoon]

Hi,

I get exactly the same message upgrading from Yabbse 1.5.5 to RC2.
I'm currently using french language but I also tried using only english.

Actually something is weird. When I uploaded SMF file to my OVH server (I'm located in France) on the 23rd, I've noticed some file had creation date changed to 24th !!! Could it be the origin of my problem ?

[[Unknown]]

I'm not sure.  Can you pm me with a link to upgrade.php?

-[Unknown]

[guytoon]

At least, I managed to upgrade to RC2.
The issue was coming from my ftp client (LeechFTP) which was uploading 0kb files.
It's working fine with SmartFTP. 
Thanks for your help