KReader not recognizing new content

Hi All

First post apart from my introduction. I haven't spent enough time here yet to know whether this is really a Kobo question or a Calibre question.

Tech details: Kobo Reader (software version: 1.9.10 (r32284 of 08 Sep 2011)) and Calibre 0.8.51 on Debian Wheezy GNU/Linux.

The problem is simple. If I send files (epub or pdf) to the Kobo using "Send to device", the job is done, but the new content is not recognized as available.

I verified that the relevant files have been copied.

Pointers as to where to look next would be appreciated.

Salud
el Mussol