I hope this solution doesn't come to you too late. I just encountered and solved the issue on my Streak you're having.
Problem is, your Picture folder where your pics and videos are located has become slightly corrupt (Folder or indexing file, etc)
-You have to connect your Streak to your PC as a USB drive
-Go to the folder "DCIM" where your images are stored
-Next go to "Camera" folder, you will see all your pics and videos
-Highlight only all the pics and video files (ignore any other files in that folder)
-Go back to the root folder (where you see the "DCIM" folder name among all the others).
-Create a folder named "DCIMnew"
-Go into the Folder and Create another folder called "Camera"
-"Paste" all of the pics and videos you "Cut" earlier
-Go back to the Root folder and rename "DCIM" to "CORRUPT"
-Go into "Corrupt" folder and rename "Camera" folder to "Pic" <--- Very important!
-Change "DCIMnew" to "DCIM"
END Part 1
(DO NOT JUMP THE GUN AND TRY TO VIEW PICS WITHOUT COMPLETING PART 2)
Now, the following steps are very important:
-safely disconnect (thru Windows task bar) the Dell Streak drive letter that appeared earlier
-Before unplugging, on your Streak's screen, choose to disconnect as a USB device
-Now, go into your Camera App (like if you were going to take a picture)
-Take 1 picture of Anything near you.
-Then, exit the camera app and go into the Gallery to view it.
END Part 2
Your Gallery will take longer than expected the first few times (might crash a couple of times in the process of loading thumbnails) depending on how many pictures you have in it. Keep going into it every 2mins.
At your convenience, you can delete "Corrupt" folder, once you've confirmed that all the pictures and videos are in the new folder, by showing up in the Gallery.