Was this test done with 1488 or 1489?
After FlashFXP has been running for awhile please do the following
From the main menu > Help
Hold down the Ctrl key
now click About menu entry
This will output application memory allocation, overhead and efficiency.
Allocated: 3.91 MB
Overhead: 1.96 MB
Efficiency: 66.6%
This shows the amount of memory allocated directly by FlashFXP, When you see the memory usage in Windows Explorer this is the combined memory of the program and all loaded DLLs and COM objects.
Updated to add Process Explorer info below
Using Process Explorer can give you a better understanding of what is allocating memory
http://technet.microsoft.com/en-us/sysinternals/bb896653.aspx
From within Process Explorer
Select the FlashFXP.exe process
From the menu View > Show Lower Pane (make sure its checked)
then Menu View > Lower Pane View > DLL (make sure DLL is selected)
Right click on the column header of the lower pane and check all options (Specifically WS Total, WS Private, WS Sharable)
This will show you how much memory each DLL loaded into FlashFXP is using and allow us to pin point what DLL if any is using abnormally large amounts of memory.