njkayaker,

Let me try to put my situation in better perspective. I've been running tubulars (mostly Vittora Corsa Elites) for years with very few flats up until returning to riding after a lengthy hiatus back in May of this year. I'm not sure what changed, but there's been a noticeable increase in the amount of roadside debris around here, and I started getting an unacceptable number of punctures. Hence the change to clinchers about 2 months ago.

Things were going just fine with the described set up until this last weekend. I got one pinch flat while on a club ride. I believe it was a ~1" step up in the pavement at a bridge crossing that got me. The next day, a similar discontinuity at another bridge crossing, this one hit a higher speed while planted in the saddle, got me the second time.

I don't know that this constitutes a trend, but I can think of several factors that might contribute. First, I had been riding very little for two years prior to getting back to cycling seriously at the beginning of this summer. During that time, I put on a bunch of weight (one of the motivating factors in my return to the sport). Secondly, as a long time tubular user, I'd gotten pretty lazy about un-weighting the bike when confronted with these sorts of relatively small bumps. And finally, in an attempt to preserve the tubular "feel" as much as possible, I've been using light weight inner tubes.

As you said, all of these are things are fixable. It's just taken discussing the issue out in the open to help me think clearly about it. Thanks for everyone's help.