[SOLVED] how to manage conversion queue?

Hi all,

I'm having the following problem with Kaltura CE server.
I uploaded five video (one after another) through the Drupal module interface, but for some reason they weren't converted so that they cannot be played.

When I inspect the Server->System status page I find that beside newBatchConvertServer there is 'in queue: 5' highlighted in blue.

When I go to 'Entries in process' page I find all the 5 videos in the status 'converting'.

The queue seems to be in a stalling state and I didn't find any way to free it from the blocking videos. I even try to stop the newBatchConvertServer service, but it doesn't answer to any stop signal.

I deleted the relative entries in the 'content' page, but this doesn't seem to affect the conversion queue in any way.

Any hint?