LAN connection speed

I have recently formatted my Hard drive after a virus and am now in a
position where everything seems to be working normally again.
However one thing that seems a little strange concerns the speed of my
Broadband/Wireless connection which is now 400Mbps using standard Virgin
Broadband.
What seems strange is that this is actually slower than prior to me
re-formatting the drive when it was consistantly 470Mbps.
Although I cannot see any reason as to why it should change I would welcome
anyones comments as to why the connection now appears to be slower than
previously.
Another 'quirk' which now appears is that when connected I regularly get the
small message window appearing concerning 'do I want to work offline' or 'try
again' . This is despite the fact that the connection is Ok and I am able to
browse through websites etc in the normal fashion.
Although more of an irritant than anything else I would once again welcome
any advice as how to eliminate the message from appearing when not necessary.

Eos.