We ran into some issue with SPminer on the p2pool after a while as well. For some reason after a long time the ping goes crazy high.
The ping is not high, it's the program that display incorrect results.. Will try to fix it in the next release
i have the same issue too i suspect the default intensity of the miner is either too high or the miner itself is unstable making the entire system unstable & causing high ping'd submitted shares,
for example i can run the web browser for a quick search while mining with any miner except SPminer which behaves as if it is very taxing on the hardware even by itself