The "solution" for the problem of marriage should not be looked for in "The Miller's Tale" or "The Wife of Bath's Tale" but rather in "The Merchant's Tale" and "The Franklin's Tale". In "The Merchant's Tale" there is a picture of a somewhat happy marriage, though it is not the marriage of Sir January and Lady May but rather the marriage of Pluto and Proserpina. In this marriage, both manage to work out active compromises which ultimately cancel out the purposes of both--Pluto wants to make Sir January aware of Lady's May's disloyalty, but Prosperina will only hear of it if Sir January immediately forgets all that he has seen--but they nonetheless manage to live with such self-negating compromises because when Prosperina says "For sothe, I wol no lenger yow contrarie." she speaks for both of them.
Chaucer's Canterbury Tales is definitely a commentary on Medieval life and a satire of the duality of people--especially those in the church who were expected to behave one way but more often than not behaved quite the opposite way.
In the case of "The Wife of Bath's Tale" and "The Miller's Tale" we have excellent examples of Medieval humor and wit. Both tales deal to some extent with marriage, but not so much with solutions to the problems presented. The Wife tells a tale about a Knight who is forced to marry an old hag who helped him answer the question, "What do women want most?" Once he gives in and decides to treat her with respect and as an equal (the motto of the worthy Wife of Bath, by the way) the hag disappears and becomes a beautiful, faithful wife. So, in essence, the answer to marital problems according to the Wife is to treat the female as an equal in the marriage--give her the respect she deserves and allow her to make decisions. Problems solved.
The Miller is a different story altogether. The "problem" in the marriage in this story is that the wife lusted after someone else, and she was lucky her husband was gullible and witless so she could pursue her lover. Rather than celebrating marriage and working on solving issues between men and women, this tale celebrates opportunity, appetite, youth, and cleverness. There is no real solution to the problem of adultery offered in this tale.
Although I have nothing to add in regards to the solutions from "The Wife of Bath's Tale" from the previous answer, I would like to expand on the possibility for a solution provided by Chaucer through "The Miller's Tale." This tale, of course, is all about adultery. Even though there can be no solution to unfaithfulness in marriage, Chaucer does give us an interesting opinion in the words of the Miller (not in "The Miller's Tale" itself, but in "The Words Between the Host and the Miller" beforehand). The Host, after warning us that the Miller is a cad and a "churl," does share these words from the Miller: "One shouldn't be too inquisitive in life / Either about God's secrets or one's wife. / You'll find Gods' plenty all you could desire; / Of the remainder, better not enquire." In other words, don't ask too many questions or you may get answers you don't want to hear. Wives have secrets, as does God, says the Miller. Both types of secrets, then, are sacred and better left unsaid. This is as close a solution as can be offered in regards to this fabliau. The irony is that the Miller has quite a few secrets, too, as evidenced by his preceding quote. He says that he doesn't "think myself a cuckold, just because . . . / I'm pretty sure I'm not and never was." The Miller's solution, then, approved by Chaucer: don't ask, don't tell. Ha!
According to Chaucer, the problem with marriage is that men are driven by lust and therefore are easily exploited by women like the Wife of Bathe. CHAUCER believes the solution is men should be more dominate and avoid women and their lust. They should be more like Jenkin. The ironic part of this is it is the exact opposite of what the Wife of Bathe wants. It is suppose to be humorous at that time period. So some of the previous responses- written above-states the teller or Alisoun/ The Wife of Bathe's views. Hope this helps