I was learning to install only one module per time, to not get plugin manager to go in timeout.
today I installed trough plugin manager the little module uc_op_reports but after that al lmain site was giving Internal Server Error.
I tryed also to grow u memory to more of 600mb but wasnt enough so then when I deleted the plugin manager main site is come back ok.
Maybe there are some conflicts between plugin manager and domain access module?