I have been experimenting and have discovered the source of the problem. webs do not work on farmland around a city. they work beyond the farmland and also within the city itself (the inner 7 hexes), but not on the farms in between. this undoubtedly created a hole in the webs that allowed naeco's stack to escape.
i don't know if this constitutes a new bug or not, but i can say for sure that i certainly did not expect it. the webs looked kinda funny after i cast it, but webs sort of always look a bit off-center to me anyways. i didn't check it with the cursor though, i just assumed the spell had worked. i apologize for this, but i was pumped at what i thought was a brilliant strategy. Hubris!
i don't know what to do, since this spell mis-firing costs me quite a bit. (i am assuming that you razed my capital, Naeco, since that is certainly what i would have done in your situation.) not only do i lose my second most valuable city, but i had rushed a production in that town, so i'm down 200 GP more, and i moved a small stack into it that was undoubtedly slaughtered without inflicting any significant damage. if i hadn't thought that the runemaster stack was trapped for at least one turn, i would not have left my capital unguarded. or at least i would not have pumped money and troops into it if i thought it wasn't safe. my whole strategy hinged on spider's curse working.
uhhh... would people be willing to consider a replay? if not that is totally ok. I just feel that i made a risky move based on a spell working, and it blew up in my face cuz the spell failed (would've been a great move if it had worked!). if this glitch is well-known and i should have known about it, then i'll abide by the turn as played, but if it was not something i could reasonably expect, then i would appreciate a chance to avoid this situation i find myself in.