This version of WED has a lot more validation than past ones did, so expect your previously "good" airport to fail validation. In particular, WED now validates that hot zones have been properly used around all runways in the ATC taxi route network. Getting hot zones perfect is very, very hard to get right by hand; the validation tool is meant to help you find the problems.
Jennifer is working on comprehensive documentation on ATC taxi route authoring; I'll link to it as soon as it's done. Our hope is that with the new docs and validation, everyone can understand how to correctly set up ATC taxi routes, and get assistance from WED to get them right.
Update: docs are up!
As some have noticed, we are not accepting uploads to the gateway from WED 1.5 betas. The issue is: if the validation code has bugs, then WED could (due to a bug) force you to upload an incorrect airport to the gateway.
I don't know when we will allow uploads, but my guess is that within two weeks we'll have a WED RC or final version that is ready to use.
For now your best bet is to use WED's new tools to get the bugs out of your taxi layout and flows.