hello,
I have experienced a general issue after updating W3; and I have seen several likewise entries here and at other places in the net.
where my blog + W3 ran perfectly, after recent updating any attempt to change settings or empty caches resulted in total breakdown, i.e. “error 500” in back + frontend.
what did solve the issue was reverting back to the prior version, 0.9.4.
I thought this might help as strategy for some people experiencing the same.
best, oliver