Great, thanks.
I have a Realtek PCIe GBE Family Controller. The download speed was fine, up to 100 Mb, but the upload was as low as 1Mb. Tried pausing the Windows Management Instrumentation, as someone suggested, which actually sort of solved this problem, but that of course was not an optimal solution.
So, following your suggestion, well it was not necessary to uninstall the suite, if was sufficient just turning the Network iControl off in the ASUS AI Suite II. That did the trick. Back up to 100Mb upload speed as well.