Thumbnails

[Mike]

I am having trouble turning some photos into thumbnails.
The photos are all the same size and type, (gif's and
jpeg's), but some I am able to turn into thumbnails and
others I can't. The icon to turn them into thumbnails
doesn't let you use it, but the image appears as its
regular size when view in a browser. Why is this
happening and what can I do about it. Thanks in advance,
this is driving me crazy.

Thanks,

Mike