Yes, you may claim the standard deduction in the federal return and itemize your Oregon deductions. In fact, if you enter itemized deductions in your federal return, your Oregon return will recognize that your itemized deductions are more than your standard deduction and generate an OR-A form in your Oregon return.
You can also look on your Oregon Form 40 and look at lines 16 & 17. Line 16 is the itemized deductions you recorded in your federal return and line 17 reports the Standard Deduction. Whichever line is largest is reported as a deduction on Line 18 of the Oregon Form 40.
This was a TurboTax database corruption problem. My 1098 for mortgage interest was entered and displayed correctly but TurboTax used a different number for my Oregon itemized deduction. I learned how to go into Info Worksheet to force display of the Oregon itemized deduction worksheet, where I discovered the problem.
I deleted and re-entered the 1098, which solved the problem.
Many thanks to TurboTax Service and Support for taking the time to teach me how to identify the problem. Case # [number removed].