Now here's an odd thing.

Installed Simple RSS - all fine.

But making any change to the configuration causes the module contents to disappear.

Removing /cache/*.spc brings makes it display again.

The feed will display until the cache refreshes and then disappear again.

Tried every kind of permission variant on evry related file.

As a last ditch attempt completely locked the cache directory by doing...

chmod 000 cache

...and this made everything work fine.

Has anyone found similar behaviour?  We'd rather have an active cache, but at least things are working.

This is not confined to Simple RSS - we got exactly the same results when using Slick RSS