... but I can login via application installed on Windows XP SP3 with no problem.
I'm using the same password when I try to login via http(s). I have been trying using all my accounts with no success.
I've iFolderApp.exe version 3.7.2.0 on Windows XP and server Debian 5.0.3 (kernel 2.6.26.5) and ifolder3-enterprise_3.7.2.
iFolder says "Please re-enter your username and password" on user side or "Unable to communicate with the iFolder server." on admin side.
A part of my log below

Code:
System.Net.WebException: Error writing request.
  at System.Net.WebConnectionStream.WriteRequest () [0x00000]
  at System.Net.WebConnectionStream.Close () [0x00000]
  at System.IO.StreamWriter.Dispose (Boolean disposing) [0x00000]
  at System.IO.StreamWriter.Close () [0x00000]
  at System.Xml.XmlTextWriter.Close () [0x00000]
  at System.Web.Services.Protocols.SoapHttpClientProtocol.SendRequest (System.IO.Stream s, System.Web.Services.Protocols.SoapClientMessage message, System.Web.Services.Protocols.SoapExtension[] extensions) [0x00000]
  at System.Web.Services.Protocols.SoapHttpClientProtocol.Invoke (System.String method_name, System.Object[] parameters) [0x00000]
2009-11-15 21:07:52,370 [-1239426160] INFO  Login - [IPaddress] CBA: key is Connection , value : keep-alive
2009-11-15 21:07:52,370 [-1239426160] INFO  Login - [IPaddress] CBA: key is Keep-Alive , value : 300
2009-11-15 21:07:52,370 [-1239426160] INFO  Login - [IPaddress] CBA: key is Accept , value : text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
2009-11-15 21:07:52,371 [-1239426160] INFO  Login - [IPaddress] CBA: key is Accept-Charset , value : ISO-8859-2,utf-8;q=0.7,*;q=0.7
2009-11-15 21:07:52,371 [-1239426160] INFO  Login - [IPaddress] CBA: key is Accept-Encoding , value : gzip,deflate
2009-11-15 21:07:52,371 [-1239426160] INFO  Login - [IPaddress] CBA: key is Accept-Language , value : pl,en-us;q=0.7,en;q=0.3
2009-11-15 21:07:52,371 [-1239426160] INFO  Login - [IPaddress] CBA: key is Authorization , value : Basic cm9vdDppZ3owZWZxag==
2009-11-15 21:07:52,371 [-1239426160] INFO  Login - [IPaddress] CBA: key is Cookie , value : ASPSESSION=EE08CC47FD66DCF8A9EF2F41; test=True
2009-11-15 21:07:52,371 [-1239426160] INFO  Login - [IPaddress] CBA: key is Host , value : myhost.pl
2009-11-15 21:07:52,371 [-1239426160] INFO  Login - [IPaddress] CBA: key is User-Agent , value : Mozilla/5.0 (Windows; U; Windows NT 5.1; pl; rv:1.9.1.5) Gecko/20091102 Firefox/3.5.5
2009-11-15 21:07:52,371 [-1239426160] INFO  Login - [IPaddress] Client Information: root, IPaddress, Mozilla/5.0 (Windows; U; Windows NT 5.1; pl; rv:1.9.1.5) Gecko/20091102 Firefox/3.5.5
2009-11-15 21:07:52,399 [-1239426160] INFO  Login - [IPaddress] Login Failed
System.Net.WebException: Error writing request.
  at System.Net.WebConnectionStream.WriteRequest () [0x00000]
  at System.Net.WebConnectionStream.Close () [0x00000]
  at System.IO.StreamWriter.Dispose (Boolean disposing) [0x00000]
  at System.IO.StreamWriter.Close () [0x00000]
  at System.Xml.XmlTextWriter.Close () [0x00000]
  at System.Web.Services.Protocols.SoapHttpClientProtocol.SendRequest (System.IO.Stream s, System.Web.Services.Protocols.SoapClientMessage message, System.Web.Services.Protocols.SoapExtension[] extensions) [0x00000]
  at System.Web.Services.Protocols.SoapHttpClientProtocol.Invoke (System.String method_name, System.Object[] parameters) [0x00000]
2009-11-15 21:07:59,286 [-1239426160] INFO  Login - [IPaddress] Client Information: username, IPaddress, Mozilla/5.0 (Windows; U; Windows NT 5.1; pl; rv:1.9.1.5) Gecko/20091102 Firefox/3.5.5
2009-11-15 21:07:59,288 [-1239426160] INFO  Login - [IPaddress] Login Failed
System.Net.WebException: Error writing request.
  at System.Net.WebConnectionStream.WriteRequest () [0x00000]
  at System.Net.WebConnectionStream.Close () [0x00000]
  at System.IO.StreamWriter.Dispose (Boolean disposing) [0x00000]
  at System.IO.StreamWriter.Close () [0x00000]
  at System.Xml.XmlTextWriter.Close () [0x00000]
  at System.Web.Services.Protocols.SoapHttpClientProtocol.SendRequest (System.IO.Stream s, System.Web.Services.Protocols.SoapClientMessage message, System.Web.Services.Protocols.SoapExtension[] extensions) [0x00000]
  at System.Web.Services.Protocols.SoapHttpClientProtocol.Invoke (System.String method_name, System.Object[] parameters) [0x00000]
2009-11-15 21:08:05,442 [-1239426160] INFO  Login - [IPaddress] Client Information: username, IPaddress, Mozilla/5.0 (Windows; U; Windows NT 5.1; pl; rv:1.9.1.5) Gecko/20091102 Firefox/3.5.5
2009-11-15 21:08:05,444 [-1239426160] INFO  Login - [IPaddress] Login Failed
System.Net.WebException: Error writing request.
  at System.Net.WebConnectionStream.WriteRequest () [0x00000]
  at System.Net.WebConnectionStream.Close () [0x00000]
  at System.IO.StreamWriter.Dispose (Boolean disposing) [0x00000]
  at System.IO.StreamWriter.Close () [0x00000]
  at System.Xml.XmlTextWriter.Close () [0x00000]
  at System.Web.Services.Protocols.SoapHttpClientProtocol.SendRequest (System.IO.Stream s, System.Web.Services.Protocols.SoapClientMessage message, System.Web.Services.Protocols.SoapExtension[] extensions) [0x00000]
  at System.Web.Services.Protocols.SoapHttpClientProtocol.Invoke (System.String method_name, System.Object[] parameters) [0x00000]
Thnx for any help