Re: FAILED: An error occured while opening a virtual disk. Verify that the Converter server and the running source machines have a network access to the source and destination ESX/ESXi hosts.

I had the same error, tried all differ version of converter and workaround. ssl=false, dns, ip ..

here's what worked for me:  Windows 2008 R2 SP1

Current environment: All 5.5. U2

1.) downloaded the 5.01 converter  installed Windows 2008 R2 SP1

2.) Disjoined the ESXi 5.5 U2 from Cluster/vCenter

3.) Run the vConverter from Source.