Before iSilo can display the tables on a page, it must format the entire page. Formatting a page includes such requirements as fitting the content to the size of the display and determining the location of each individual piece of content. In the case of tables, formatting also involves calculating the width and height of each cell of the table. Without this information, it would not be possible to display the content of tables in tabular format.
The amount of time needed to format a page depends on the size of the page. The more content the page has, the longer it takes. So the behavior you should expect to see is that tables on shorter pages display quicker than pages on a larger page. If it seems like tables do not show up, then you either need to wait longer or ask the author of the document to make the pages of the document shorter (in particular, the pages with tables). One other possibility though is that if there is not enough memory to store the formatting information for a page, tables will not display.