Vault client can't connect on through one of my ISPs

[jlorenzon]

I'm using Vault 5.0.3 (18802). For silly reasons we have two ISPs. The vault client will connect through one, but we plan on discontinuing this service.

When trying to connect to the same server through the other, we receive

"No server was found at the specified URL. Please verify your network settings using the Options dialog under the Tools menu in the Vault GUI Client. Web Exception: The request failed with HTTP status 417: Expectation failed."

Going to the vault server in a web browser, everything looks fine (weirdly, the front page reports the wrong version - 4.... - the vault server was recently upgraded. The web service reports the correct version though, and it works over the other ISP).

I have tried enabling and disabling HTTP proxies within the vault client configuration and on the client computer, and trying all of the network settings in different configurations. I assume the ISP is running some proxy configuration that Vault is incompatible with. Is this likely to be the problem? Is there some way around this?

[lbauer]

Are you able to login to the Vault server using the web client, or are you only able to hit the Vault homepage?