Drupal 7 doesn't work on cheap hosting. (This is a secret designed to annoy people when they discover).
This is the conclusion I have reached after loads of developer videos failed to tell me: they use dedicated servers or their own hard discs.
The problem seems to be memory limits which have risen by mistake for no particular reason. Just as a Ryan Schama talks about "project creep" in his lecture, Drupal 7 has a Server Memory Creep towards needing an expensive host which nobody advertised or planned: it just happened and caught a lot of people out.
For those on the borderline there are three cacheing products
I find this frustrating because I did a bit of research over a year ago, trying to find out how to make a low-magin, loss making business sell more and at the time Drupal 6 / Ubercart was the fastest-loading software and I searched for days to find the fastest cheapest host. Now the calculation is a different one which rules out this host and this whole school of software together, and probably Drupal software altogether. I have spent over a year trying to learn the XYZ thing while shopping carts have forked and re-built themselves. Now I discover that I should have gone with Virtuemart in the first place. Such is life. If you read about an american going crazy and shooting people in a shopping mall, maybe they had just tried to install Drupal. Or maybe it was looking at the awful overpriced stock in TKMAX that did it. One of the two.
What other annoying things are there in life? Youth is wasted on the young? Trades unions let you down when you get an unfair dismissal? Radio station editors don't like news or music? Maybe I should petend to be a Bonobo Monkey and live in a park where zoo keepers will feed me.