Are you on shared hosting?
Is compress js and css off? Though that might not explain why it worked before and not now.
Many posts on the forum. My experience was that it was the hosting. MODx making too many requests, and the IP getting temporarily blocked.
Wait a few minutes, then try to load the manager again. If it loads completely, then navigate around to chunks resources etc, and see if it trips up again and goes blank, or parts of the tree are no longer visible.
Thank for your answer.
Compress js and css are on. I put them to off for testing, put the same problem.
Yes I am on shared hosting. I will contact my hoster for that problem and if it give me a decent explanation, I will share it with the modx community
discuss.answer
Here is the solution, the technician disable (again) the Mod_Security module on my account, because it was causing a conflict with ModX.
Thank