Upload file error (small files)

[kameleon20]

I have something strange.

I've succesfully set up the roundcube (1.2.2) within my company.

If I try to upload a psd or pdf file, but a png, doc, docx does not work except when it has a certain size (784933 Bytes is the exact minimum required to succesfully upload a file).
Anyone any experience with it, and knows the solution?

[JohnDoh]

is there any more info in the roundcube or php error logs?

[kameleon20]

No it does not log any errors about this.
Strange thing is, everything under the size of 784933 Bytes can not be uploaded, but above seems to be no problem, and it sends the bigger files without any problem.