TYPO3 Core

Carlos, which version of tt_products did you use? In general the dependencies should be defined in the extension. If you think this is a Core issue, please tell the TYPO3 version you're using.

I could reproduce a very similar bug.
tt_products and mbi_products_categories, which depends on it, are shown in the EM and installed. But in the frontend you get this error message.

TYPO3 Fatal Error: Extension key "/serverpath/typo3conf/ext/tt_products/" was NOT loaded! (t3lib_extMgm::extPath)

However the localconf.php shows that tt_products is installed.
The EM backend for tt_products shows:
Active status:
The extension is installed (loaded and running)!

To reproduce it:
Install tt_products then mbi_products_categories. Then copy another tt_products there and overwrite the former one, e.g. by renaming. Delete the typo3conf/temp_CACHED.. files and all caches.

To reproduce the first bug:
Install tt_products 1.2.7 and not table and fh_library. Then use the EM and install tt_products 2.5.2 from TER or import from t3x file.

I could also reproduce a very similar bug.

I have installed a newer version of tt_products (not from the TER) and have some troubles with tt_products and static_info_tables, which is just a suggest for tt_products.
Both are shown in the EM and installed.

I get the following error message in the frontend when dropping a product into the basket and clicking into it:

TYPO3 Fatal Error: Extension key "/serverpath/typo3conf/ext/static_info_tables/" was NOT loaded! (t3lib_extMgm::extPath)

but the localconf.php shows that static_info_tables is installed and also in the Typo3 Backend Extension Manger the Active status shows up:
The extension is installed (loaded and running)!

This is a SVN patch request:

There is only a simple error message 'TYPO3 Fatal Error ...' but no debug info.

Solution: Display the full call path and you will save a lot of hours of inverstigation time.

tt_products users must use fh_library 0.0.19 in the future with an additional check if tt_products has been installed. But strangely this is being called from tt_products.

Related to: http://bugs.typo3.org/view.php?id=5919

This is an important patch. Please check this in as soon as possible!

If you have installed mbi_products_categories and then it happens that you deinstall tt_products, you end up in a blocker and all the TYPO3 website has gone!
If you happend to be no TYPO3 expert, then you are completely lost now.

The patch changes the error message to:

Backtrace:
/html/typo3/typo3_src-4.3.2/typo3/backend.php : 28
/html/typo3/typo3_src-4.3.2/typo3/init.php : 180
/html/typo3/typo3_src-4.3.2/t3lib/config_default.php : 555
/html/typo3/typo3conf/temp_CACHED_psb7fd_ext_localconf.php : 1226
/html/typo3/typo3_src-4.3.2/t3lib/class.t3lib_extmgm.php : 185
TYPO3 Fatal Error: Extension key "tt_products" was NOT loaded for extension mbi_products_categories! (t3lib_extMgm::extRelPath)

So you at least will know that it it the extension mbi_products_categories which has required tt_products which you did uninstall a few minutes ago.

The patch provides a good help, but does not cure the problem (deleted dependencies and conflicts).
Maybe a discussion in Core List can bring better solution (which then can directly be integrated)?
What do you think, Franz?