Hi,
According to your description, my understanding is that the cursor disappeared in Word 2010. Was this issue occur with every file or the particular file?
If this issue only with the particular file, please try the method that I copied here:
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Copy the entire document into a new, freshly opened, blank document, leaving behind ALL the formatting. DO NOT transfer any of the old formatting to the new document.
After the "text only" is copied into the fresh document the cursor resumes its proper functioning and can always be seen as it should be when using the arrow keys.
Then manually reformat your document the way you want it to be formatted. (Font type, font size, tabs, italics, line spacing, etc...)
Any new text you copy and paste into your document, make sure you paste it as text only without its outside formatting or you run the risk of re-corrupting your document and losing your cursor again.
Reference:
http://superuser.com/questions/195645/disappearing-cursor-in-word-2010
Please Note: Since the web site is not hosted by Microsoft, the link may change without notice. Microsoft does not guarantee the accuracy of this information.
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If this issue with every file, even a black file, please try to delete the Word data and Word option key and check if it helps. (PS: If you did not try this method)
http://support.microsoft.com/kb/921541
Hope it's helpful.
Regards,
George Zhao
TechNet Community Support