Well, there are certain ways that you can lessen the annoyance of eratta:
1. You can accept that it is simply an unavoidable part of playing 4e with Character Builder, and either stop playing 4e, or stop using character builder.
2. You can contact WotC and inform them of how Character Builder could be better in regards to handling eratta, which might (possibly, in the long term) be implimented.
3. You can have a person who keeps an eye out on the eratta coming out, and informs any persons affected by the eratta of the changes... I find that simply by hanging out here, I learn about nearly all the eratta that comes out within a day or two of it doing so, as there is inbaribly a thread here for each new eratta release, or for stealth eratta as it is discovered.
4. You can use the Rules Compendium (and/or DDI) as your "go to" source for general rules, and the CB printed cards for specific powers. This should reduce the problem you are experiencing as a DM checking up on rules issues that do come up - to my knowledge, it contains 99.9% of the general rules (its missing the ritual rules, and the "10ft drop" move action that was in the pre-essentials eratta release) and none of the general rules have been erattaed since the Rules Compendium.
5. Don't impliment rules "surprises" mid game - if something comes up as possibly changed, promise to look at it between games, and simply play it the way it used to work for that session. This will prevent the "loosing 30 minutes of planning" problem you described.
6. Allow free retrains out of elements affected by errata. This is easily done in Character Builder by changing it in the "Powers/Feats" window(s) rather than by the retrain option under "Manage my character".
7. Houserule elements that you don't think should be changed. For example, I still let Pacifist healer (since fixed by eratta) work when they had removed the divine keyword from Healing Word, and the Flaming Weapon (stealth eratted by DM's Kit) to still change the damage type for implement powers, to keep it consistent with the Frost and Force weapons the group has (they are all plot items, and it doesn't make sense for them to work differently).
I've done #3 to #7 with my group, and it has greatly reduced grumbling from the player who hates eratta in general (he's an MMO player who has suffered from multiple nerfs in that hobby - he's ALSO our most RAW player) - the "free retrain" has particularly helped in this, and has led to said player swapping what were previoulsy strictly better powers for ones that much better suit his character.