Are the pictures you are adding held on a flash drive, external hard drive or other device that may have limited memory/space available. The software attempts to compress the pictures and may run out of room attempting to.

If the files are on an external device move them to your hard drive, change the picture gallery to that location and try this process again.

If the pictures are on the computer hard drive, space could also be an issue but is not usually likely. If the pictures are on the hard drive, there may be an issue with the pictures...they are too large to compress or have attributes that limit this process. Try opening the pictures in a picture program and shrink or compress the size and save them and then attempt the process again.