Typo3 4.7.7 (php 5.4.43) странная проблема с раширениями.

[Николай Сипко]

Если долго мучиться, что-нибудь получится. Могучим методом тыка:
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1. Clean typo3temp/ folder
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2. Clear tables
Use with care! Clearing tables here can have a negative impact on your site functionality. You could log out all users, delete all their basket data, and lose logging information!
Some database tables in TYPO3 CMS hold semi-temporary data that is not deleted when clicking "Clear all cache" in the backend. Those can be cleared here, effectively removing all rows from it. This can be useful in rare cases.
be_sessions
cache_imagesizes
cache_md5params
cache_typo3temp_log
fe_sessions
fe_session_data
sys_history
sys_lockedrecords
sys_log
tx_extensionmanager_domain_model_extension
tx_rsaauth_keys
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3. DB check
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Предварительно я бы удалил (хотя бы на время) UIXplorer.