Problems with the Asset Revaluation

Hi! I have a problem with AA,when i run the Asset Revaluation.

If I run at 31.01.2010 i have this message:

AF 100000000 No Revaluation Posted for Period 001 / 2010

Instead if i run in december, i have this error message:

8Z812 No hay valores a revalorar p.act.fijo 000100000000 0000

Cantidad activos fijos tratados: 1

Cantidad activos fijos sin revalorización y sin error: 0

Which is logical because the asset values only in January.

Any idea why I can not revaluate the asset??

thank you,

H.