I save one word letter on my machine and tried to open it. I got the below error:
Word experienced an error
Try suggestions:
* check the file permissions
* Make sure there is sufficient free memory
* Open the file with the text recovery

Then I go to the properties of word document and in custom tab I changed any custom property value and then apply.

Then surprisingly word document opens perfectly.

It is not related to any specific custom property value but I think changing any value will set some permissions of the document.

Please let me know if any common settings are there in word doc which can i change and let the word letter open properly without error.

I do not want to set the custom properties of each and every document.

Does this happen for every document, or just some? If it's every document, see:
http://www.gmayor.com/what_to_do_when_word_crashes.htm

__________________
Cheers,
Paul Edstein
[Fmr MS MVP - Word]

This is happening with some documents only.

OK, it seems the affected documents have some form of corruption. Corrupt documents can often be 'repaired' by inserting a new, empty, paragraph at the very end, copying everything except that new paragraph to a new document based on the same template, closing the old document and saving the new one over it.

__________________
Cheers,
Paul Edstein
[Fmr MS MVP - Word]