[TYPO3] no_cache=1 is driving me nuts

[hartmut]

Hi,

not for the first time I have the problem, that all my pages are set to 
no_cache=1.

For testing purposes I finally created a page on root level with its own 
template, stripped to the bone.
Setup:

config.admPanel=1
page = PAGE
page.10 = TEXT
page.10.value = HELLO WORLD!

Additionally I set
"Static template files from T3 Extensions:"
to "never include"

Cleaned up database and typo3temp.

Still adminPanel says no_cache=1.
WTF?!

What else can I do?
Is there a extension, that could help me find what causes cache-disabling?
Any secret recipe?

TIA
hartmut