You probably have turned off calculation
You can quickly test with F2 then Enter and if that works
then that is a possibility. F9 will recalculate, there are more
powerful recalculation shortcuts
http://www.mvps.org/dmcritchie/excel/shortx2k.htm#calc
which you might try if the following fail.
1) Turn Calculation on tools, options, calculation (tab), calculation: automatic
2) Make sure you are not in formula view -- would not apply here because
you say it is fixed when you close, which is another indication of calc turned off.
The first workbook that is opened controls whether calculation is on or off.
You might need to close the open workbooks except for your personal.xls
with your macros and unhide that (window, unhide) before fixing option,
then of course hide your personal workbook again so macros will be available
in other workbooks when they are opened.
A macro that abnormally terminates would be one way that calculation gets
turned off, and of course you could have turned it off manually. A misbehaving
add-in can also turn off calculation and fail to turn it back on -- but add-ins are
usually written by people who take a bit more care -- but it certainly does happen
with add-ins as well.
http://www.mvps.org/dmcritchie/excel/slowresp.htm#checklist