Friendly URLs not being friendly

Got a problem that's been bugging me for a while. I have four sites on the same server, all running Revolution and all with Friendly URLs set up. However, friendly URLs obly works on one of them. I also have a few sites running Evo on the same server and all those are working fine.
The revo versions are all different:
2.0.6 - Works
2.1.1 - Doesn't work
2.1.3 - Doesn't work
The ones that don't work just go back to the index page (not the error page).
I've gone through the friendly URL guide (http://rtfm.modx.com/display/revolution20/Using+Friendly+URLs) but that hasn't helped.
I've set up the htaccess files and System Settings/FURLs exactly the same as the working site for each site... I've cleared caches, refreshed, and tested on different computers and networks but no change.
Has anyone else had this problem and if so, did you manage to fix it?

Is there anything you can think of that's different about the site where they don't work (upgrade rather than fresh install, in a subdirectory, extra contexts, etc.)?

You've probably tried these already, but:

- Manually delete all the files in the core/cache directory
- Clear the browser cacha *and cookies*
- Check the path in the modx_workspaces directory in PhpMyAdmin
- Make sure the filename is .htaccess, not ht.access
- Check the rewrite base line in .htacces
- Make sure mod_rewrite is enabled on the server
- Make sure you have this in all templates:

Thanks Bob.
All are fresh installs, all are in the root dir of the site. There is nothing different in any of the installs other than the versions. I have tried all those you suggested except:
- Check the path in the modx_workspaces directory in PhpMyAdmin
Will check that in the morning and let you know how I go.

Checked the path in the modx_workspaces directory in PhpMyAdmin and all ok.
I've checked other sites running 2.0.6 and they work also.
I've attached 2 screen shots of the settings of each... is there anything there that looks out of place?

I had a similar problem with revo 2.1.3-pl and furl (with lighttpd). They worked, and I couldn't get the running again after I disabled them in the manager for debugging purposes.

Deleting /core/cache and making a new cache directory did the trick.

Thanks Bob for this hint!

Cheers
Frisco

crewmark, I don't see anything in your settings that would cause a problem. Redirects seem to be me to be touchy in recent versions.

Have you tried with FURLs off?

Thanks Frisco... I tried dumping the cache manually but only dumped all the files within the cache directory, not the actual directory itself so will try that.

Thanks BobRay, with FURLs off it all works fine except it uses the index.php?id= addressing. It's strange that it works on some sites but not on others... I am going to try deleting the whole cache dir first and if that doesn't work I'll copy one of the sites to a local test environment and see if there is any difference.

Will keep you updated.

If it works with FURLs off, it usually indicates a problem with your .htaccess rewrite rules.

(You did rename ht.access to .htaccess when you had FURLs on, right?)

Yes, the htaccess has been set up and renamed.
I've tried using exactly the same file as one that works and no go. I've followed the instructions at http://rtfm.modx.com/display/revolution20/Using+Friendly+URLs and no go either hence why I'm so confused. I was going to update them all to the latest Revo version but thought I'd wait for the 2.2pl first.
Thanks for helping with this.

The only thing I can think of would be if that particular install is in a subdirectory.

Another thought: If you used FTP to upload the site, one or more files might have been missed or corrupted. It happens more often than you might think.