apache 2.2 - svn Error when commiting-Access denied: 'foobar' MKACTIVITY MYREPO:

I'm currently working with Apache and SVN with ActiveDirectory Authentication. The user is using TortoiseSVN client.

I should point out that I have 2 repos with same name and different mapping but redirected to the same "user url" since the permissions are the same for both repos.

eg 'http://mysrvr/svn/foo/bar/corge' and 'http://mysrvr/svn/foo/corge'

or 'http://mysrvr/svn/foo/bar/corge and' 'http://mysrvr/svn/foo/grault/corge'

This 2 repos thing is replicated with 8 "repo pairs" and the remaining 7 are working just fine.

Here is my error:

Commit failed(details follow):

access to
'/svn/myDir/MYREPO/!svn/act/65bf494c-a66a-4f45-870e-d988f691a45d'
forbidden

Finished!

It's not permissions, since the user foobar has rw access and he has successfully checked out the repository. This error happens on commit.

Things that would help to orientate to a precise solve:

Other repo pairs are doing fine. And the permissions are the same.
My svn administrator user can do at the same local PC as the troubled user that commit.
UPPERCASE/lowercase URL isn't the problem, i've checked
NTLM and Active Directory aren't the problem either since he has access to the other repo with the same permission file.
Other users of the same repo are experimenting the same problem. While I can still do the commit at their local PCs. (just as if they had no writing permission)
Here are the Apache logs:

Apache error.log

[dd mm 12:38:02 2011] [error] [client 10.x.x.x] Access denied: 'foobar' MKACTIVITY MYREPO:

[dd mm 12:39:40 2011] [error] [client 10.x.x.x] Access denied: 'foobar' MKACTIVITY MYREPO:

[dd mm 12:39:54 2011] [error] [client 10.x.x.x] Access denied: 'foobar' MKACTIVITY MYREPO:

Apache access.log

10.x.x.x - foobar [dd/mmm/yy:12:38:02 GMT] "OPTIONS /svn/myDir/MYREPO
HTTP/1.1" 200 198

10.x.x.x - foobar [dd/mmm/yy:12:38:02 GMT] "PROPFIND /svn/myDir/MYREPO
HTTP/1.1" 207 667

10.x.x.x - foobar [dd/mmm/yy:12:38:02 GMT] "MKACTIVITY
/svn/myDir/MYREPO/!svn/act/65bf494c-a66a-4f45-870e-d988f691a45d
HTTP/1.1" 403 266

svn_activity.log

[dd/mmm/yy:12:34:20 -0300] waldo
commit r2

[dd/mmm/yy:12:39:07 -0300] fred status
/src/trunk r1447

From the svn_activity.log I can deduce Apache catches and bounces the access, given that there is no foobar access at time-frame exposed previously.

So, hoping that the data i've collected is useful to solve this... any ideas?

P.S. It looks like this link but I've got more data. :)