I've been having a heck of a time getting some of my TYPO3 4.* sites to upgrade to TYPO3 6.0.

First trouble was just updating a system from 4.* to 6.0.0 using the install tool. The install tool ran fine but now editing content elements is broken. I just get a gray screen when I try to edit any content elements.

I also tried to do a pagetree export from a TYPO3 4.7 site and then import it into a fresh TYPO3 6.0.0 install. That didn't work either. I got the error "uid of fileusage (sys_file_reference) has to be numeric."

I'd like to do upgrades as cleanly as possible, but I may require some hacks to accommodate my particular setup.

Update: Using the advice of Dmitry Dulepov, I turned on the configuration setting that tells TYPO3 to display errors to me on my site.

Now, instead of seeing just a blank gray screen in the backend when I try to edit a content element, I see an error where the blank space used to be:

Fatal error: Call to undefined method TYPO3\CMS\Core\Utility\GeneralUtility::intInRange() in /home/xxxxxxxxxx/typo3conf/ext/lorem_ipsum/class.tx_loremipsum_wiz.php on line 106

It's pretty obvious that this means there's a problem related to the lorem ipsum extension.

I next went to the extension manager to disable the lorem ipsum extension.

Now, editing content elements works as it should. My problem wasn't really the upgrade to TYPO3 6.0.0 after all. It was just an issue related to the lorem ipsum extension.