Try disabling all scripts.
Try changing the zoom level of your browser.
Although scripts may work on other worlds, it is possible the special nature of Vet servers mean they don't. There are so many scripts that it is impossible to predict what they will do on a Vet server. Similarly, the zoom level of the browser affects how things are displayed, this may be enough to see the opposition. Does this only happen in PvP or is it also happening occasionally when attacking the forgotten (either bases, camps, outpost or Guardian bases on hubs?