WiFi sync has always been very occasionally flaky... but usually re-launching iTunes solves the issue (MacPro desktop, iPad mobile device). Now it doesn't work AT ALL and nothing I have tried has brought it back. Somehow it has only been in the last few days; when was the last iTunes update?
Read something about a "AppleMobileDeviceHelper" being some process that one can quit and relaunch, but no such thing shows up in Activity Monitor, nor in file content search for the whole machine, nor much from apple's website.
My desktop is hard wired to the router, it works just fine (i.e. connecting to the Net). My iPad also continues to work just fine, connecting to the outside.
And yes, I disconnected and re-connected (i.e. Airplane mode) to no avail.
Now I see 98% of the complaints out there are from M$ OS users, but I use OS X because I believed "it just works." So what do we do when "it just doesn't work" and all we get is stony silence from Cupertino?