Ken, I'm sorry, but I can't isolate the problem. It's stably reproduced only deep inside my control tree. For example, when I move the uploader control to the parent of its current containing user control the bug disappears. But I need the uploader exactly in that place where I have it.

 

IMHO the deletion of temporary files is the key for this problem. The uploader is placed inside an updatepanel. And files are not deleted after partial postbacks caused by uploading of additional files. But they are stably deleted after the first full postback. Why could it be like this? Could you tell me any possible reasons?

 

Thank you for your quick response.

 

Georgii