I have findout ChilkatDotNet2.dll library is located in sitecore bin folder and can't be load in case if enabled 32-bit app support in app pool. I removed this library and it seem like web site is working fine. Is it necessary for Sitecore to have it?
The library might have been installed on your Sitecore instance with a module (I believe the Email Campaign Manager uses it). If that's the case, the module installation files probably contain both a 32-bit and a 64-bit version and it would be up to you to use the correct one for your system.