As title says, when I try to load any mod and/or master files, I have an infinite sequences of error messages. Like these:

MASTERFILE: ===========================================================
MASTERFILE: LOCALIZATION: Lookup failed for ID: 0x00012584 from strings file: STRINGS/Skyrim_ENGLISH.DLSTRINGS
MASTERFILE: LOCALIZATION: Lookup failed for ID: 0x0001257D from strings file: STRINGS/Skyrim_ENGLISH.DLSTRINGS
MASTERFILE: LOCALIZATION: Lookup failed for ID: 0x00012561 from strings file: STRINGS/Skyrim_ENGLISH.DLSTRINGS
MASTERFILE: LOCALIZATION: Lookup failed for ID: 0x00012554 from strings file: STRINGS/Skyrim_ENGLISH.DLSTRINGS
MASTERFILE: LOCALIZATION: Lookup failed for ID: 0x0001253A from strings file: STRINGS/Skyrim_ENGLISH.DLSTRINGS
MASTERFILE: LOCALIZATION: Lookup failed for ID: 0x00012540 from strings file: STRINGS/Skyrim_ENGLISH.DLSTRINGS
MASTERFILE: LOCALIZATION: Lookup failed for ID: 0x0001252F from strings file: STRINGS/Skyrim_ENGLISH.DLSTRINGS
MASTERFILE: LOCALIZATION: Lookup failed for ID: 0x00012587 from strings file: STRINGS/Skyrim_ENGLISH.DLSTRINGS
MASTERFILE: LOCALIZATION: Lookup failed for ID: 0x00012583 from strings file: STRINGS/Skyrim_ENGLISH.DLSTRINGS
MASTERFILE: LOCALIZATION: Lookup failed for ID: 0x0001252A from strings file: STRINGS/Skyrim_ENGLISH.DLSTRINGS
MASTERFILE: LOCALIZATION: Lookup failed for ID: 0x0001254E from strings file: STRINGS/Skyrim_ENGLISH.DLSTRINGS
MASTERFILE: LOCALIZATION: Lookup failed for ID: 0x0001256F from strings file: STRINGS/Skyrim_ENGLISH.DLSTRINGS
MASTERFILE: LOCALIZATION: Lookup failed for ID: 0x0001251E from strings file: STRINGS/Skyrim_ENGLISH.DLSTRINGS
MASTERFILE: LOCALIZATION: Lookup failed for ID: 0x0001255B from strings file: STRINGS/Skyrim_ENGLISH.DLSTRINGS
MASTERFILE: LOCALIZATION: Lookup failed for ID: 0x00012566 from strings file: STRINGS/Skyrim_ENGLISH.DLSTRINGS
MASTERFILE: LOCALIZATION: Lookup failed for ID: 0x00012523 from strings file: STRINGS/Skyrim_ENGLISH.DLSTRINGS
MASTERFILE: LOCALIZATION: Lookup failed for ID: 0x0001256E from strings file: STRINGS/Skyrim_ENGLISH.DLSTRINGS
MASTERFILE: LOCALIZATION: Lookup failed for ID: 0x00012522 from strings file: STRINGS/Skyrim_ENGLISH.DLSTRINGS
MASTERFILE: LOCALIZATION: Lookup failed for ID: 0x00012562 from strings file: STRINGS/Skyrim_ENGLISH.DLSTRINGS
MASTERFILE: LOCALIZATION: Lookup failed for ID: 0x00012553 from strings file: STRINGS/Skyrim_ENGLISH.DLSTRINGS
MASTERFILE: LOCALIZATION: Lookup failed for ID: 0x00012547 from strings file: STRINGS/Skyrim_ENGLISH.DLSTRINGS
MASTERFILE: LOCALIZATION: Lookup failed for ID: 0x0001255E from strings file: STRINGS/Skyrim_ENGLISH.DLSTRINGS
MASTERFILE: LOCALIZATION: Lookup failed for ID: 0x00012574 from strings file: STRINGS/Skyrim_ENGLISH.DLSTRINGS
MASTERFILE: LOCALIZATION: Lookup failed for ID: 0x00012571 from strings file: STRINGS/Skyrim_ENGLISH.DLSTRINGS
MASTERFILE: LOCALIZATION: Lookup failed for ID: 0x0001254F from strings file: STRINGS/Skyrim_ENGLISH.DLSTRINGS
MASTERFILE: LOCALIZATION: Lookup failed for ID: 0x00012558 from strings file: STRINGS/Skyrim_ENGLISH.DLSTRINGS
MASTERFILE: LOCALIZATION: Lookup failed for ID: 0x00012560 from strings file: STRINGS/Skyrim_ENGLISH.DLSTRINGS
MASTERFILE: LOCALIZATION: Lookup failed for ID: 0x00012546 from strings file: STRINGS/Skyrim_ENGLISH.DLSTRINGS
MASTERFILE: LOCALIZATION: Lookup failed for ID: 0x00012576 from strings file: STRINGS/Skyrim_ENGLISH.DLSTRINGS
MASTERFILE: LOCALIZATION: Lookup failed for ID: 0x0001254C from strings file: STRINGS/Skyrim_ENGLISH.DLSTRINGS
MASTERFILE: LOCALIZATION: Lookup failed for ID: 0x00012556 from strings file: STRINGS/Skyrim_ENGLISH.DLSTRINGS
MASTERFILE: LOCALIZATION: Lookup failed for ID: 0x00011B5F from strings file: STRINGS/Skyrim_ENGLISH.DLSTRINGS
MASTERFILE: LOCALIZATION: Lookup failed for ID: 0x00011C71 from strings file: STRINGS/Skyrim_ENGLISH.DLSTRINGS
MASTERFILE: LOCALIZATION: Lookup failed for ID: 0x000126C3 from persistent strings file: STRINGS/Skyrim_ENGLISH.STRINGS
MASTERFILE: LOCALIZATION: Lookup failed for ID: 0x000126C4 from persistent strings file: STRINGS/Skyrim_ENGLISH.STRINGS
Assert

File: C:\_Skyrim\Code\TESV\TES Shared\misc\BGSLocalizedString.cpp

Line: 1566
LOCALIZATION: Error opening or reading strings file.
MASTERFILE: LOCALIZATION: Zero entries or empty block size read from strings file STRINGS/Update_ENGLISH.STRINGS. Strings will be missing.
Assert

File: c:\_skyrim\code\tesv\bssystem\BSTSmartPointer.h

Line: 167
Null pointer

And after, editor crash. How can I fix this?

Are you trying to load Dawnguard? If so I believe you need to extract the strings from Dawnguard's BSA and put them in the Strings folder.

Nono, I haven't Dawnguard.

Hmmm. Do you have the english version of the game or another language? The CK is only in english so it may cause issues if you don't have the english strings?

I have the game in italian. Anyway, seems to be a very popular problem, searching on google. And seems to be not solutions.

I have this issue with an English version of the game. I have Dawngaurd but was not trying to load it.