[>BKA< T Wrecks]

I just saw KWo also had this problem, so I finally got my lazy arse up to post this bug:
On some maps (mainly maps with larger waypoint files, like 500+ nodes), I noticed that when standing on a certain node, the node itself and also the surrounding nodes and connections start to blink or even disappear entirely for some seconds. The problem is always restricted to one small region on a map and will stay there, i.e. it's always the same area that's affected. Waypoint fuctionality is 100% ok, and in game, bots move just fine. It's only the display that gets disturbed somehow. It can also happen that some or many of the blue radius bars around a WP will vanish from sight.
This is relatively harmless, but quite weird. I experienced it on cs_industrywest and cs_ncruins2 so far. Both WPs are mine - and ok. I have other maps with far more than 500 nodes, and there I don't get this problem at all. I haven't seen this occur on maps with small WP files so far, but since it appears to show quite rarely, that doesn't necessarily indicate anything. the sys is a Win98SE 1.5 listenserver...
Does anybody have even the remotest clue as to what might cause such a strange error?