Error: Internal Exception

Error: Internal Exception

Hi Team,

I'm trying to convert a page to a pdf file and send the attachment in an Email. It is working fine but sometimes it gives an error saying Internal Exception. 
I got to know that this error is due to the time limit it takes to execute the invokeURL.

page_url = <URL of Page>
file_obj = invokeurl
[
url :page_url
type :GET
];

is there any way to solve this problem? 
Note: Not everytime I'm getting this error, only when it takes time to execute invokeURL the error occurs