Software update?
If the "1K" that you refer to is the image width, and if you're saving to JPEG format, your image quality setting may have changed. JPEG files can be saved at a number of different quality levels, with lots of compressing giving you a small file containing an ugly picture and no compressing giving you a huge file containing a pretty picture.
The most you can attach to any one post is 1000KB, which is the size of the file, not necessarily the size of the picture in pixels.