Setting the max number of simultaneous jobs to one and seeting the job priority to low seems to have solved the problem. Just tried converting 20 books and there was no hanging or any other problems. And as suggested, I have excluded Calibre from my norton antivirus scan. Thanks a lot guys.
Now that i have that major headache resolved, i have questions about 2 small problems. I wanted to overide the image icons used in Calibre. In the manual it says that i should not change the images stored in the resources sub-folder of the calibre install location as my changes will get overwritten the next time I update calibre. And that i should instead, go to Preferences->Advanced->Miscellaneous and click Open calibre configuration directory, create a sub-folder called resources and place the files i want to override in it.
When I went to the open calibre configuration directory, there was already a sub-folder called resources and another folder called images within that. And there was another sub-folder called generate_images within the images folder. As instructed, I placed my images ( that had the same names as the images in the images stored in the resources sub-folder of the calibre install location) , inside the image folder but it did not change the image icons in calibre to mine even after i restarted calibre. Why is this ?
Also, since that did not work, I tried replacing some of the default images in the resources sub-folder of the calibre install location with my images that had the same name . ( I know that the images will be overridden back to the default when i update calibre in future ) That worked for some image icons like library.png and book.png but when i replaced the catalog.png with my own catalog.png, the image icon for the catalog disappeared. Why is this ? Does the pixel size have to be the same or something ?
Also is there any way to change the roman numerals used to show the series info when generating the covers to normal numbers ?
P.S On a separate note, Calibre is an amazing program and i seem to be able do more and more with it as i learn more about it. Kovid, just wanted to let u know that u have done an amazing job.