Thanks,
In our case, we had been using W3 Total Cache for quite some time with no issues (and with object caching enabled), it's just been recently that the blank pages have been a problem.
I did try and disable plugins, and didn't find any differences.
However there have been some changes, including some experiments with MySQL caching settings to improve in/out performance, and so that could be a factor.
I'm trying it now with object caching disabled (been running with W3 Total Cache disabled completely, which has ended the appearance of white pages).
Afraid I don't have the resources or the training to fully test every configuration, but we'll see how it goes.
Again, appreciate the insights.
kip