Thank you for your post.
I am having difficulty replicating the problem.
Using FileMaker Pro 10.0v3 under Windows XP SP3, this is what I have done.
1. Create a new database file, Test.fp7 with the following two fields:
a1 (Text - Validation - a1="Y")
2. I create a Value List "YesNo" with two custom values "Yes" and "No".
3. In Layout Mode, I double-click "a1", Display as: Drop-down List, and Display values from: "YesNo".
4. In Browse Mode, I created a new record, selected the "Yes" value for a1, and the cursor jumped to a2. No error message.
5. Pressing the tab key took me back to a1, the value list appeared, and I was able to click in the field and change the value from "Yes" to "Yessss".
6. When I finally committed the record, then I received the message: "a1" is defined to contain only specific values. Allow this value?
7. I removed "a2" from the layout. Now, when I put my cursor in "a1", the value list showed up, and selecting a value left me in "a1" where I was able to change the value. Clicking outside the field committed the value and the validation error message appeared.
What am I doing differently than you?
I just went back to my test DB and went down the list of validation options, testing each in turn.
The following options exhibited this inconsistent behavior
Member of Value List
Maximum Number of Characters
"By calculation" did not.
Of course, FMP's built in "invalid criteria" validation while in Find Mode (my original example) also triggers this premature validation test.
Murphy's Law... The one option I choose is the only option that doesn't fail. :-)
I have verified the other Validation options, and I confirm your findings.
I have forwarded this information to our Development and Software Quality Assurance (Testing) departments for review and confirmation. When more information becomes available, I will let you know.