Solution:

If you are using EMM386, you will need to configure it to avoid the address used by DOC 2000 (set by Jumpers). Otherwise, the memory management will attempt to use these addresses, causing unreliable operation. The line in config.sys file that invokes EMM386, might be the following: Device=EMM386.EXE RAM X=D000-D1ff This excludes an 8KB range from D000 to D1FF ( the default address)