Ok, so Vigilad's solution from earlier in the thread appears to work. Instead of accessing your games through the store (either via the game page or your download list), go to your download list through the XMB (Playstation Network -> Account Management -> Transaction Management -> Download List). The copy available there appears to be valid. I was able to download and install Super Stardust HD that way. Infamous is currently downloading, and the trial icon isn't on the bubble, so it's promising that it will work.
I will try the thru the XMB when I get home. But I have the same problem as of 12/19/12. All the Welcome Back Games won't install cause the PS3 thinks they are PSP games. I have Dead Nation, Infamous, Star Dust and some other that I don't remember right now, but yes all of those are Welcome Back Games and I'm experiencing the same problem with all of them.
As stated before the XMB path Playstation Network>Account management >transaction management> Download List
option does work but what I am kindof curious about is why even though this works, has it become a requirement to begin with. THis is still happening after several months of it becoming a known issue and re-downloading from the store itself or even from the Download history from within the PS Store results in it showing up as a PSP/vita game. Even more rediculous is that you must completly re download the file via the xmb path and completly delete the one from the store as it is essentially junk data.