Hi,
I guess you don't have this error since the beginning,
so tell what have you done in the meantime, installed something, changed server settings, anything?
I am asking a question as a doctor, I have to know a reason of pain to cure you.
Before the problem appear, i did two things :
- in server config, change upload max size to 4MB for download last version SPPB
- update to last version Joomla