I have already started a thread here:
https://www.mobileread.com/forums/sho...d.php?t=133273
But now I can finally verify that my problem (dictionary search takes 5 seconds instead of instant lookup, pages turn much slower) definitely has to do with calibre conversion...
I got a mobi file from the web and it worked perfectly well on my Kindle (either copied to the documents folder directly or uploaded onto the Kindle via calibre), everything was snappy and worked like I charm...
The same file then, converted with Calibre showed the behavior I knew, dictionary lookups took forever, page turns longer too...
I'm not so sure if anyone can help me as it seems I'm the only one having this problem but maybe someone could suggest a foolproof method of getting the conversion right (I already reset everything to factory settings, to no avail) or even, if that's the only thing that works for me, a different conversion tool so I can finally transfer my ebooks onto my Kindle (3) and actually use them properly...
Thx a lot folks!