That's a packet loss all right. If you only experience this during a specific map, one question and two differential diagnostics pop up in my head.
The question is, do you experience this in one or in all ET mods? This may lower the possibility that a file may be corrupt (however, this is a likely cause!)
The second dd being simply that your video card sucks. You mention that you only noticed this since a few days. Have you recently installed new things on your PC, or changed certain settings? Had a windows/asus/whatever update? There may be a driver mismatch or you may have overexerted your computer. There may be a .dll conflict with a new file you downloaded, however, I am not sure if ET even uses .dll's Too lazy to check
My advice at this point would be:
-Check map in other mods
-Check for similar packet loss in very sizeable maps with lots of moving objects and players
-Reinstall your ET