No, I don't think that this is a memory-issue. Server is rather fast, running on 64bit and 8 MB Memory.
I noticed some other cause:
Bulk-Uploads seem to depend on the photo details description!
I explain here with the recent photos of the ropeway to Mine La Mejicana
- Single-upload works with any lenght of description.
- Bulk-upload works only with description up to 570 characters including space.
- Bulk-upload with a description longer than 570 characters (in this case 1412 characters) fail and "Error 404" appears.
- In second screen of bulk-upload I can add all description without any problem.
So it seems to me, that the problem is the description?