Something error with the score

That's not a bug, that happens when something happens to your system (computer) clock and while it's off by several hours, days, weeks, months or years, BOINC contacts the project and gets new info in on credits & RAC. Then later the system clock gets reset to the normal time and all's fixed, but for the line in the statistics.

This can easily be fixed though. First and foremost, exit BOINC completely.
BOINC Manager->Advanced view->File->Exit->Check "Stop running tasks on manager exit?" (or similar wording)->click OK.

Navigate to your BOINC Data directory. Default in Windows 7 at C:\Programdata\BOINC\
Find the statistics_einstein.phys.uwm.edu.xml file and open it with a text editor, such as Notepad. No need to use an XML editor.

In it you'll find time stamps in Unix clock format.
Example given:
[pre]
project URL

1326844800.000000
16000.000000
756.709427
16000.000000
757.380135


1326931200.000000
16000.000000
644.494901
16000.000000
645.063585


1327017600.000000
17500.000000
706.009674
17500.000000
706.513130


1327104000.000000
18000.000000
738.735278
18000.000000
739.227172

[/pre]
See those day entries? Find the one that's the either the highest or the lowest --depending on what your clock did, go forward or backwards in time-- and remove the whole .. part around that day.

If not sure, you can use an Unix time converter to check the values to check what all the values are.

Then save the file (just with File-Save or CTRL + S), exit the file and then restart BOINC (Start->All Programs->BOINC->BOINC Manager).

That should do it.