Proftpd 'no such user' error

[Nuklear]

I have obtained following error with ftp accounts

I have 2 servers. A server S1 has WHM. A server S2 has not. My domain DOM points to S1 and some of DOM’s sub domains points to S2.

I created ftp account named ‘s1acc’ on S1 using cpanel. Some time my ftp account works fine but one day a have obtained error in ftp connection. Analyze of logs showed that proftpd reports error ‘no such user “s1acc”’. I removed it and tried to create another account but the same error appears. ftp.DOM points on S1 as cpanel requires.

Could anybody help?

[Nuklear]

Any ideas?