Try this...
I have Photoshop.com Mobile installed on my Incredible and had the same issue. Not sure exactly how I fixed it but I did play with several settings.
1. Formatted my SD card (back-up your stuff first).
2. Open the camera app and find the "Settings" option and select "Storage", set it to "Storage Card".
3. Take a few pics, then open up the PS.com mobile and it should automatically recognize the pictures you just took.
4. I may have rebooted my phone after step 2, not entirely sure.
Edit: Picasa (on my desktop) will not recognize any pictures I have on my SD card (when connected as "Disk drive") unless it is in the DCMI folder. That may be what PS.com mobile may be looking for. So, if you have pictures saved at the root directory or in a folder named "Pictures" (or whatever) on the root directory, it may not see it. I hope this helps you.