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I updated one of my installations from 1.6.6 to 1.7 and all seemed well.  The "system information" all passed. (with one "!" for current php 5.2.11) all seemed well until I tried to add new content.  Then I got these failures:

Warning: fopen(/home/abc/public_html/bvg/tmp/cache/contentcache.php) [function.fopen]: failed to open stream: Permission denied in /home/abc/public_html/bvg/lib/classes/class.contentoperations.inc.php on line 568

Warning: fwrite(): supplied argument is not a valid stream resource in /home/abc/public_html/bvg/lib/classes/class.contentoperations.inc.php on line 569

Warning: fclose(): supplied argument is not a valid stream resource in /home/abc/public_html/bvg/lib/classes/class.contentoperations.inc.php on line 570

I looked at the folders and it looks to have the same permissions as another cmsms (1.6.6) installation.  (Which work fine.)
For instance the /tmp/cache/contentcache.php file in both instances was set as 0644.  But out of desperation I changed the permissions of the 1.7 version to 0777 and then the problem 'seems' to have gone away.  But I'm not comfortable with my guessed at solution.

On a separate issue.  In this instance (1.7) the editor icons, tinyMCE, (the area above the content window) is blank.  It seems like I saw this before a couple of years ago but can't remember (or find) what caused it.  -thx-

Try a Clear cache from admin area - global settings - advanced.

And for Tiny:
Tiny module have a list of posible solutions in its help section
I.e. try to do a    reset all settings to default  in Tiny admin - advanced.

Thanks for everything.  Tiny now is smiling at me!