Thanks. What I read from that thread is that possible hypotheses for my problem are:
[*]I'm not in the video section of XMB
[*]The directory depth is more than 8
Both of these aren't it -- I'm in the video section, and the directory depth below the file system root is 3 and below the directory shared to the PS3 it's 1. I also don't get any network errors, and after rebooting the PS3, everything is fine again... More ideas?