Networking :: Suddenly Slow Access To Server Folders

I upgraded my PC from Windows 7 Ultimate (64-bit) to the Windows 10 'replacement', which is Win10 Professional (64-bit). All went extremely well, no problems, the Windows 'upgrade' retained my settings, all 'mapped' network drives were there, everything was totally great. I easily accessed, created and and saved new documents to folder locations on the server with no 'hesitation' whatsoever.

HOWEVER... SUDDENLY, within the past eight to ten days, where I once had virtually 'immediate' access to shared folders on our aging Windows Server 2003, I now seem to be required to 'wait' for upwards of 8-10 seconds before folders on the server are 'accessible'. For instance: I'm setting up this year's 'fiscal year' folders for my business invoices on the server. As I attempted to create these folders, I had to 'wait' to be able to 'see' and then be able to access the 'Invoices' folder on the shared drive. Then (as I always have done) I 'right-click' within this folder to create the new folder for FY2016 and once again, it takes 8-10 seconds to be able to create this folder, but eventually this is successful. Then I created 'sub-folders' within this folder (IE: "QTR 1") with no delays..

But then in creating a sub-folder within this sub-folder (IE: 01-JAN), there's the same 8-10 second delay. Continuing on with the creation of folders through the full year, SOME are created immediately - OTHERS suffer from this same 'delay'. It is almost as if my PC must 're-negotiate' with the server - determining 'rights' (?) - I dunno, but it truly frustrates me.... I know full well that I MUST replace this old server OS, since Server 2003 is 'dead', but - well, I simply haven't taken the time. Time is money - and I don't have enough... so you know what gets 'first efforts'.

But since I have been operating like this since BEFORE Windows XP was even released (albeit, yes, on a Windows NT Server, back then) with nothing even resembling this 'hesitation' ... Why now, after this 'mandated' upgrade to Windows 10, is this 'hesitation' appearing in simply accessing what was once practically "immediate'..? The whole network is all CAT-5 'gigabit' Ethernet: both of the switches are gigabit, server connection is gigabit, my PC is gigabit, cripes even the NAS is gigabit (yet another 'storage location' on the network...) and where the NAS was 'slower' earlier, it is now 'faster' to access and store on the NAS instead of the Windows Server.