can't upload .jpg files

I was running Dolphin V6.1.6 on a shared server with PHP 5.3 ... the users can't upload .jpg files (.png and .gif files load fine). how to solute the question????

 Was, as in past tense?  What has changed for your server?  Did you check the admin for allowed file types?

You may have forgot to compile php with the GD library.  .jpg may have been removed from the photos upload module or you do not have the jpg mime type set..  just a few things to look at.

Fixed,  downgraded to php 5.2 and all was well...  switched back to php 5.3 and the error appeared again.

In the end I switched off GD library and used image magick instead problem solved....