Update.php does not assign any particular update (update.php is not working properly)

I have the same problem, but I still continued through the update.php.

Then I got the following error:

An HTTP error 501 occurred. https://(mywebsiteurl)/update.php?id=43&op=do

When I tried to click on the error details nothing loaded.
When I looked at the watchdog logs, there was no error reported.

I tried the update.php a second time and now there was a selection to do an update.php action for the rules module, but the above error still happens.

This time, however, when I clicked the error details I received the following:

warning: array_pop() [ function,array-pop]: The argument should be an array in /var/www/html/update.php on line 314.

The update process was aborted prematurely while running update # in .module. All errors have been logged. You may need to check the watchdog table manually.

The # and the .module are typed exactly as they appeared.
It seems that the update.php failed to return a number and a module name!

Okay, the problem I mentioned has been confirmed to not be a rules issue.
I cannot say anything about the original posters case other than that it may be the same issue as mine.

Heres what I discovered.

At some unknown point, drupal's update.php changed its "content-type" http data from application/xml to text/plain.
Or at least that is what I am thinking.

The problem comes into play when I have mod_security enabled.

I have had a similar problem in the past and the solution was to add "application/xml" to line 68 of modsecurity.d.orig/modsecurity_crs_30_http_policy.conf file.

This has been working for months now and I have had no problems running update.php, until recently.
There apparently was an update such that update.php no longer works with the mentioned mod_security change.
This bug was simply revealed by my attempting to updatie the rules module.

The solution is to append the new content-type: text/plain to the rule in the modsecurity rule file.
Here is the working line in the file /etc/httpd/modsecurity.d/modsecurity_crs_30_http_policy.conf

SecRule REQUEST_HEADERS:Content-Type "!(?:^(?:application\/x-www-form-urlencoded(?:;(?:\s?charset\s?=\s?[\w\d\-]{1,18})?)??$|multipart/form-data;)|text/xml|application/xml|text/plain)" "t:none"

So this seems to be not a Rules issue.

There is no update for Rules and Rules Admin UI, only for Rules Scheduler. Just run update.php to clear the cache, you don't have to select a particular update in your case. Fago has added that to the Release notes (hi from Drupalcon Paris ;-).

I have been debugging a problem with update.php using a thread you can find using "6.14 install" since the problem occurred after an install of 6.14 on one of my systems. I'm adding the final result here in case what's happening in your case is related.

I finally worked around it by changing browsers, but oddly this browser worked fine up until 6.14.

Here are the error messages obtained from Seamonkey error console:

Warning: Error in parsing value for property 'display'. Declaration dropped.
Source File: http://revere.umina.lan/drupal/modules/system/defaults.css?U
Line: 43

Warning: Error in parsing value for property 'display'. Declaration dropped.
Source File: http://revere.umina.lan/drupal/themes/garland/style.css?U
Line: 646

Warning: Error in parsing value for property 'display'. Declaration dropped.
Source File: http://revere.umina.lan/drupal/modules/system/defaults.css?U
Line: 43

Warning: Error in parsing value for property 'display'. Declaration dropped.
Source File: http://revere.umina.lan/drupal/themes/garland/style.css?U
Line: 646

At this juncture I've solved the problem by using a browser that handles these errors differently.

If you think this is a ModSecurity issue see #320532: Batch API not working when http policy of mod_security is enabled. for the related issue.

Updated component.