I recently upgraded to Joomla 1.5.20 from 1.5.11.

I have JMS 1.1.8 with patches 1.1.3

I then installed Virtuemart in the root page. The Check Patches page of JMS showed missing JMS-related changes in Virtuemart.

I went ahead and clicked Install to install the patches. It suddenly logged me out. When I came back, I noticed that I had lost the multi-site functionality. No matter whichever site I go to, it always defaults to the root site.

I have now restored the files back and it works as before. However, I would like to know how I can get the Virtuemart updates for JMS installed.

Which did you restored.
This is not clear.
Did you mean that you have restore joomla to 1.5.11 ?

When you install VM on the master website, this is normal that JMS reports that a patch must be installed.
Does the installation of the patches succeeded ?
You say that you are logged out but this is normal.
The question is does the patches were installed or does that all the patches were uninstalled ?

For your information, you are still using a old JMS 1.1.x and the latest 1.1x were the 1.1.24.
See the FAQ for the procedure to update your JMS.
www.jms2win.com/faq#sec-122

Perhaps this is the time to upgrade to JMS 1.2.x.

Which procedure did you used to update Joomla ?
Did you un-install the JMS patches before to update Joomla ?

The behavior that you describe seems to indicate that all the patches were un-installed.

Perhaps you had a permission error somewhere to install a patch.

The problem is when I install the patches, I am losing the multi-site functionality. I get only the root site no matter whichever slave site I try to access.

That was why, I had to go back to 1.5.11 (which I had backed up).

The method I used to upgrade was
a) Downloaded the 1.5.11_to_1.5.20 upgrade from Joomla.
b) Compared the files in the upgrade with my current 1.5.11 files and transferred all JMS related patches to the corresponding files in the 1.5.11_to_1.5.20 package.
c) Applied the 1.5.11_to_1.5.20 package via file copy.

After this, I see multisite showing the patches as it were before (only missing patches was VirtueMart)

Can you tell me a safe way to apply all patches in 1.1.8 ?

I have now followed the upgrade method I listed earlier and got to Joomla 1.5.20 but with the missing patches for VirtueMart. I am afraid clicking the Install patches button will throw me into the same situation as before. Is there any other way of getting the VirtueMart patches into the appropriate Virtuemart files ?

I can not reply to you on JMS 1.1.x.
All I can tell you is that starting with Joomla 1.5.16 and higher, we have recommended to use the JMS 1.2.27 or higher.

www.jms2win.com/faq/change-history-v12x/...y-joomla-1516-php-53

The behavior that you describe to me looks like a patch that can not be installed and that roolback (uninstall) all the patches.
As you say that only VM is the one listed, I suppose this is the patch on VM that should be the problem.

This is strange that the VM patch should be installed if you just update Joomla and you don't receive any Joomla file to install.

Perhaps you could also check that you have the permission to install the patches and that you don't have file with a different owner or protected to would not accept to re-install the patches.

If you want that we have a look on your server, we have a billable support that you can order at www.jms2win.com/download?page=shop.produ...35&category_id=1