Pawn Limitation - Please Advise.

In two consecutive games (usually towards the end) I intend to move a pawn out two spaces forward and it rejects my move and only advances it one space. 

I looked into rules such as en passe and such but have yet to find an explanation for this.

Lag is very unlikely via my connection.

Post a link to the game, with a move number. It's possible that you were in check and the single pawn advance blocked that check.

http://www.chess.com/livechess/game?id=430338493

move 25/26.... wait a minute thats not the the en passant is it?

Yup. You solved it yourself.

ahh i always just wrote that off as lag and got frustrated. thanks guys.

love this game.

Still doesn't explain your original complaint because the pawn does move two spaces but then gets taken en passant. Don't understand what you mean by it only moving one space ?

here's the next game where the same thing happend.

Inverse en passant?

http://www.chess.com/livechess/game?id=430345327

move 33 in the next game

it must be he did it twice in a row.

Yes, in both games the pawns were taken en passant

Here´s a great study for delivering mate via e.p. in various forms; it´s by Kenneth Howard from 1938, I got it from Wikipedia.

The main line is without e.p.´s; variations 1 and 2 use them excessively!

               Kenneth Howard, 1938 - White to move, mate in three.

Bxc6, and Black has no way of preventing Bxd5#.

Thanks sapient - I´d found it and edited it into the diagram after posting, that´s why the original question (what happens after 1... d5?) isn´t there any more. Thanks all the same!