No images created/shown (due to transliteration?)

I face the following problem: I have a CCK type "Blog" which has an ImageField "Article Image". I use that image along with the title, teaser, etc. to display it in a Views Slideshow (using Views Rotator module). Now my site is a multilanguage site, English and Thai. I was facing the following problem:

From two test-articles, only one was showing the article image in the slideshow. I could switch the site language so my View would load the article data from Thai language and still the image would be shown. However, for my second test article, in both languages the image was not shown. I tried to remove and re-upload the image but that did not change anything.

I had a look on my FTP server and saw that:
(1) the /files/pictures folder was holding an image for my first article as well as an image for my second article. I was able to identifiy that because I am using tokens to generate a file name like --.. However, for my second article, the filename looked rather cryptic: 6-รักเรานั้นมั่นคงส่งใจหา อดีตที่พาน-20100325-main.jpg (there was another image with same nid as I removed and reuploaded the image to see if it changes anything as mentioned above).
(2) the /drupal/sites/default/files/imagecache/blog_image_310x205/pictures folder contained only a file corresponding to the first article but nothing for the second article.

So I guessed it was due to the cryptic filename (which obviously is the automatic transliteration of the node title in Thai language), I deleted all images for that node, went back to the English version of that node and uploaded the picture again: Now all images were created, having English/Roman letteres filenames and everything showed up.