Duplicate entries unto cache

Is this still an issue?

Yes.
This problems sometimes happens to me, but I don't know why.
I think it could be because I'm using i18n, but I don't have sure.

Just to inform that it's happen in 4.6.9

After further checking I've found also "user error: Duplicate entry 'locale:en' for key 1" that was marked "won't fix".

http://drupal.org/node/38505#comment-60708

The real mysql specific solution is in 4.7 but it makes PHP 4.3 a strict requirement and we won't change requirements in a minor release that would cause havoc. (It's still only recommended to have PHP 4.3.3 for 4.6, without search module you can get away with less)

Because I do not quite understand what is the "real solution" I've checked the code and found that the change was the adition of db_lock_table() and db_unlock_tables() functions.

Resuming:
* add the functions db_lock_table() and db_unlock_tables() in database.mysql.inc
* change the cache_set() to be like the one in 4.7 bootstrap.inc

I marking this as critical, because this bug disables the option to use the cache system in a site with a language different from the base one (locale:en)

I'm assuming this hasn't been fixed and forwarding it to 4.6.10.

4.6 is no longer maintained. Closing.