Error using MSHTML objects

[g.difalco]

When I use the following code

Htm el = htm ( "some parameters here...getting a <TABLE> element")
MSHTML.IHTMLTable t = +el
mes t.rows.length

everything works. But if I use a pointer variable...

Htm el = htm ( "some parameters here...getting a <TABLE> element")
Htm* elp = &el
MSHTML.IHTMLTable* t = +elp
mes t.rows.length

...I get the error message "invalid interface pointer. Use _create or other function to create or get object".
Why?