Could you please try something for me
Run this test
http://www.dslreports.com/tweaks
After you run the test near the bottom of the page directly below "Still stuck? copy/paste this url:" copy and paste that url into your reply.
I know it's alot of effort but I'd really be interested in seeing the results with hotfix 893066 installed and uninstalled. Please be sure to list which is which.
Based on that we should be able to determine what you need to change to get FlashFXP working with the hotfix installed.
Also if your MTU is 1500 and you use DSL you might try lowering it, to for example 1458. The above test should give you some recomended MTU values.