Most servers have max. 2mb file limit for uploading via http, and the LightMart template installation file is over 2mb.
This might be the reason of failure.
Try other installation methods.
First of all, with using your FTP software, upload the installation zip file to your server, then in the joomla backend(extension manager),
Try one of these alternative installation methods:
- Install from Directory
- Install from URL
Attachment Pasted_Image_5_28_13_5_43_AM.gif not found
I am 99% sure it will work out, but if still no luck, let me know. I will take a look at it more deeply.
Regards.