System cannot find interface.MPQ?

I downloaded the 2.3.4 client from excalibur this morning and after downloading I was able to get on to the login screen.

A few hours later after waiting for the realmlist to be announced I tried to open up the game again but this time it came up with the error

"Failed to open archive interface.MPQ: the system cannot find the file specified."

After trying unsuccessfuly to figure out what the problem was I decided to reinstall the client but it had the same error again.

So a little later a decided to uninstall and reinstall for a third time...and it still doesn't work.

Why is this popping up and why was I able to get on with no problem earlier but then this started happening?

Edit: just redownloaded it again and it worked...guess 4th time the charm