Replace Optional Hyphen
Replace Nonbreaking Space
Unfortunately, MS really messed up on this.
Unless fixed in Office 2010 SP1, you may need to redo the files.
TRY 1: Try to save the file. You’ll
need to enable saving when you do this. See if that works.
TRY 2: You can copy and paste the
merge document into a new document to make it work.
TRY 3: Reconnect the merge document
with the data file. Hopefully it will work. It is flaky.
TRY 4: You can copy and paste or save
with a new name, the data file. DO NOT COPY TABLES (but you can copy the
contents of a table into the new datafile). Then
reconnect the merge document to this data file.
NOTE: Particularly, if you do macros
on your data file—it is going to mess up mail merge. L
Another bug in MS Office 2010. To fix until Office 2010 SP1 or Windows 7 SP1 fixes this—download this complicated set of fixes (you may need to install several updates to make it work).
http://support.microsoft.com/kb/980681
Grr. This is because the connection between the merge document and the data file allows only 255 characters and even the 255 is iffy because tabs and commas and paragraph returns can mess up the count (as far as I can tell).
Solution: Change how your merge document is connected to the data file.
Go into Options and make sure the Confirm file format conversion on open is checked.

Exit from Word and restart.
Open your merge document.
Click Select Recipients, Use Existing List
When that happens, it will ask you what kind of a connection you want.

Choose MS Excel Worksheets via DDE (*.xls) (yes, this will work on .xlsx files)
If the DDE option isn’t there—check “Show all”
Your merge will now show all of the information in your data file even if more than 255 characters long.
Press Ctrl and F keys at the same time.
A few people complain that when you search, you can't use the doc map/navigation pane (the search covers it up).
To fix that, do this:
right click the ribbon.
choose customize the ribbon.
click keyboard shortcuts: customize in the lower left.
choose the home tab on the upper left
on the right, find "EditFind" and select it
in Press new shortcut key, type in something like Ctrl and 4.
--NOTE--DON'T USE Ctrl and F because you need that keystroke to show the navigation panel when in reading mode.
from now on, press Ctrl and 4 and you are set to go with the old Find dialogue box.
when you search, you can't use the doc map (the search covers it up).
to fix that, do this:
right click the ribbon.
choose customize the ribbon.
click keyboard shortcuts: customize in the lower left.
choose the home tab on the upper left
on the right, find "EditFind" and select it
in Press new shortcut key, type in something like Ctrl and 4.
--NOTE--DON'T USE Ctrl and F because you need that keystroke to show the navigation panel when in reading mode.
from now on, press Ctrl and 4 and you are set to go with the old Find dialogue box.
The problem is that your cells are formatted to show information a specific way.
Go into Format Cells (Format, Format Cells) and change to the way you want it. Often, changing to Text solves the problem.

Press Shift when you click to unflag.