Memory alloc exception

Hi list,
I get this error when running a SQL statement in my Java application.
ERROR: Invalid memory alloc request size 1683636507
Location: File: d:\pginstaller.auto\postgres.windows-x64\src\backend\utils\mmgr\mcxt.c, Routine: MemoryContextAlloc, Line: 779
Server SQLState: XX000

I think it has something with to do with PostgreSQL
This is how I had my postgrsql.conf:
shared_buffers = 128MB
#huge_pages = try
#temp_buffers = 8MB
#max_prepared_transactions = 0
#work_mem = 6MB
work_mem = 64MB
#maintenance_work_mem = 64MB
maintenance_work_mem = 64MB

Then I changed to this postgrsql.conf:
shared_buffers = 4096MB
#huge_pages = try
#temp_buffers = 8MB
#max_prepared_transactions = 0
#work_mem = 6MB
work_mem = 256MB
#maintenance_work_mem = 64MB
maintenance_work_mem = 256MB

And got this error instead:
Org.postgresql.util.PSQLException: AnI/O error occurred while sending to the backend.

Any ideas?

Kind regards,
Paul