Choc, I with the others betting that she's overwhelmed and this is a cry for help around the house. My W is a stay at home mom, and I work from home so I see what she goes through. It is truely the most thankless job one can imagine. No task is ever done (if it is, it needs to be done again shortly anyway), the work is rarely appreciated, often times it is undone by the rugrats before anyone who could appreciate it even gets a chance to see it. It isn't a paid job, so there is no tangible reward for the effort, and it is a round the clock job, no going home at the end of the shift. Worse yet, the 'working' moms who go off during the day to mini-vacations from the family each day and earn a paycheck tend to think stay at home moms have abundant free time so they should be the ones to do the school room mothers, PTA, cub scouts and so on. W has on several occasions been told by a 'working' mom things like, no they couldn't send a liter of apple juice in to school for the party, they are "way too busy, one of you stay at home moms should do it" (where do they think the money comes from anyway?). Sorry 'bout the rant.
It helps tremendously if they have another adult to talk to. If she isn't already, encourage her to join a neighborhood mother's group. You can check with your church, or there is usually some sort of Newcomers club in town. Ask around, I'm sure if she knows any other stay at home moms someone knows of something.
More importantly, take some of the load off her. Your job is probably only 8 hours. Give her some time off in the evenings by putting the kids to bed, checking the homework etc. Remember, hers is a thankless job; Tell her frequently how wonderful she is and what an excellent job she is doing and how it makes you feel so good to have a wonderful wife willing to do this for you and your children. Being a stay at home mom is probably the greatest thing you can do for your kids, but it is also probably the hardest job there is, especially in today's world where most of your neighbors are not, and there is no thanks at least until the kids have grown up and realize what a great gift you have given them by being a stay at home mom. Another possibility is have her sign up for a fun class with your local continuing ed. My W goes to a quilting class one evening a week for about 6 weeks a couple times a year...mostly a way for her to get away from the job now and again.
--GGB who is realizing he doesn't do enough to support his SAHW, but is trying.