Accessing events on external drive in iMovie '11 on Lion

I have my iMovie events stored on my external harddrive (located in a Synology NAS). It worked like a charm with iMovie '11 on Snow Leopard.

I then received my new MBP with Lion and the external drive is not showing. I cannot thus access my events which is pretty annoying as it prevents me from using the application...

Here is what I see in iMovie:(see edit 2 for new state)
I previously had my external drive below the Macintosh HD one.

My external drive is correctly mounted before launching iMovie:

It has the iMovie Events folder at root level (and as I said, it was correctly detected under same iMovie version on Snow Leopard).

I tried mounting it using afp: but result is the same.

Any help appreciated as I don't get what could have changed between SL and Lion for this.

edit: Same with volume now mounted using NFS:

The list in iMovie stays desperately empty...

edit 2: something new! My NFS mounts are now visible in the list (probably coming from an update of iMovie inbetween).
Problem is that they are still empty and with a yellow warning sign, without any tooltip on it...

Lion turned off an older and less secure method of authenticating AFP connections, which a lot of third-party vendors of NAS devices were using, including Synology. Synology have made available a beta release of their new firmware which fully supports Lion (as long as your Synology device was made in 2008 or later).