Right now the BlackBerry 9780 is not supported to work with the Slingbox. You can find the list of supported devices here,
Is there any way to contact slingbox.com support directly (i.e. - not through this forum) for an answer?
Sure you can, Contact Technical Support
Tried it again, but still get the same error. I think the reason it worked for you is because if you already install it with OS5, then upgrade to OS6, the apps that were already installed via OS5 continue to work after the upgrade. But if you try to download the app from Sling via OS6, it recognizes the new browser and gives you the error that tells you it's not compatible and can't be downloaded. I have a few other apps myself from my old 8900 that I downloaded from App World that are now on my 9780 when I used "switch devices" and although App World says that some apps aren't available to me, they are listed within App World, and still work on my 9780.
Well I've been MORE than patiently waiting. Phone came out nearly a year now. No sign of support for OS6 / 9780 phone support from Slingbox. OS7 phones out now, no Slingbox app there either. I was going to rant about how companies are purely interested in higher profits above all else these days but instead suffice to say, I guess Slingbox (and other companies) feel it to be in THEIR best interest to develop only for the latest trends instead of supporting otherwise loyal customers. So be it. If that's truly the case with Slingbox, then in retrospect, I'm glad I didn't decide to purchase a Slingbox back when I was using my Blackberry 8900 which was supported. Because I would have ended up having some truly great hardware (a Slingbox, my BlackBerry 9780, and my wife's new BlackBerry 9900) with no way to watch it on those devices.
Sincerely But Sadly,
* Edited to observe Slingbox Answers Forum House Rules by Moderator. *