It sounds like you have your Activation Rules at one of the settings that allow a chance that your stack becomes fixed-in-place if your commander fails his Activation Roll. (Good for you!) When a general rolls inactive under these settings, he is forced to make a second Activation check: if he fails a second time his entire stack is fixed in place for the turn (he gets a red stripe on his portrait that turn).
McDowell, like most early Union generals, sucks because of his low STRAT rating, which Activation checks are based on. Early Union generals are rarely active two turns in a row and regularly get fixed in place. Generals who were inactive on the previous turn get a penalty to their next activation roll, so it is common for 3 STRAT or lower generals to become inactive or fixed for several turns in a row.
Early Union aggression is constrained by their constant inactivity. It is easy to lose stacks by overextending and being unable to escape when your semi-competent commander becomes fixed in place for two turns.
Turning this rule off strongly favors the Union, as it negates the CSA's main early advantage (Activity).