Thumbnail issues

I’m new to WordPress and set up a blog today. I uploaded image files and the default for thumbnails was 150×150. I changed it down to 100×100 and proceeded to uploading the image files again. I was successful with 5 images, but something went wrong for the 6th one. It uploaded as 100×66.

I deleted it and uploaded a bigger size image thinking the original size of the image was just too small. But the thumbnails would not appear as 100×100 anymore, only as 100×66 no matter what image file I would upload. What when wrong?

I did not change anything in the media settings. I’ve been trying to figure it out, even reverting to the original 150×150 thumbnail size. But all the image files I’ve been uploading since come in as 100×66 and it’s not what I want.

I don’t know what else to do and it is getting frustrating. I hope someone can help me out. Thank you!