Hi Mehul,
first of all: Welcome! You are owning a NAS1000? Well, I think you found your destination here

.
There are different solutions to your problem, cause its a pretty well known one. Thats the good news.
But there are different reasons for failing in upgrade - some are really serious. Thats the bad one.
Well, do not panic now! At the beginning theres 3 questions to your NAS (You might set the answers into your signature so the next time you will post a question theres no need to ask for. And you will, I am sure

)
1.) What was the Firmware you run befor the upgrade?
2.) Which Firmware did you take and where does it come from?
3.) How do you connect your NAS? Peer2peer with a Win-PC or a LinuxStation or a MAC or ist there a Router between?
Did you made a Backup of your stored data? No? Do so via USB Connection. It will work.
When you use a router: Look into the DHCP Entry an search for a assigned IP. Maybe this is your NAS.
If you´ll find it try this IP.
Greetz. Snoopy
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Der Mensch ist das wichtigste und kostbarste Peripheriegerät einer Computeranlage.
myStuff: NAS2001+4220(1000Gb-ext3)+Dlink524+KabelD. (120 Mbit)