App installation bugaboo

I think that this is more of an Apple/iPad/Safari issue than an AIR for iOS  issue but there's no-one smart enough on Apple forums to answer it so here goes. I'm developing an app for an industrial client and distributing in-house test versions to my client's test team. We're using my client's Enterprise Development Certificate from Apple, and a private server and, usually, distribution is a piece of cake.

One of the team member's iPad will now not download the current version of the app. On this iPad Safari navigates to the download page correctly, but when the download link is tapped Safari says 'Cannot connect with [the name of my test server]' (which in this case is the same server that we're reading the download page from). I think that this is the message that you might ordinarily get if the .plist were not in good order or if it pointed to an ipa that was either not there or mis-named.

No other test-team iPad has this problem. We've made sure that there's enough available storage on this iPad, we've cleared profiles, cleared the Safari cache, updated the names of the .plist and .html files that we're using, all to no avail on this particular iPad. Other iPads have no prob with this. And the app's ipa bundle loads just fine on this device via iTunes.

Has anyone here seen this kind of problem before? Any suggestions besides arranging for a fatal accident for this particular iPad?