Raw and large jpg problem

[WestFalcon]

I don't shoot raw but would like to do so. I shot raw and large on my 20D. The thumbnail for the jpg appeared but the raw was in a box with a feather on it...no thumbnail. Then when I tried to open it, it says that it will not open it because it is the wrong kind of document. I have photoshop CS and I have opened them before . Any idea of the problem?

[PacAce]

Do you have the ACR 2.4 plug-in installed in PSCS? If not, that'll explain why you can't open it.

[WestFalcon]

i don't think i have that plugin but I have opened raw images before...sometimes it will let me.