The Omaha, Neb.-based company placed a note on its site warning that it had canceled the extended hours session, a company representative said, adding that Ameritrade canceled all stock trades placed during the session.
"The extended hours session was canceled because the market destinations were unable to facilitate trades," the company said in a statement.
Ameritrade began after-hours trading last fall. The session takes place from 4:15 p.m. to 6:30 p.m. EST.
The representative declined to identify which trading network was having problems, but the company has said previously that its after-hours partners include Island ECN, MarketXT, Knight Securities and the Chicago Stock Exchange.
MarketXT, however, has not yet begun its partnership with Ameritrade, said Gary Berger, MarketXT's vice president of technical services. Representatives for the other trading networks were not available for comment.
Charles Schwab, which also offers after-hours trading, did not have problems during last night's session, a company representative said. E*Trade and Fidelity Investments representatives were not available for comment.