If you try to create a new rank profile that has an illegal name (such as a name that contains angle brackets), the schema update will fail on the FAST Search servers, but you will not receive an error message in the PowerShell console. Subsequent index schema updates might also fail without any error message in the PowerShell console.

After applying SP1, such an index schema update attempt will instead return an error message of the type "Rank-profile "<rankProfileName>" is invalid, rank profile names must be lower-cased".

Note that the rank profile name must only contain lowercase ascii characters.

If you have problems with an index schema update, or suspect that an update is not applied consistently on all servers, you can run the following command on the administration server:

   cd <FastSearchInstallFolder>\index-profiles
   bliss -C deployment-ready-index-profile.xml

The command will re-apply the internal index schema representation to all servers in the FAST Search for SharePoint farm.
In the above error situation, the output may give an indication of the error cause.

In the case of an illegal rank profile name (in this case named "<test>"), the output will look something like this:

[2011-01-18 08:44:26.582] INFO       systemmsg Compatibility check: Rank-profile "<test>"is added. Reload of configuration files required.
[2011-01-18 08:44:26.582] INFO       systemmsg Running index-profile update with compatible index-profile
[2011-01-18 08:44:26.645] ERROR      systemmsg RankConfigBoostTableWriter unable to generate '': IOError: invalid filename: boost-tables\<test>_anchortext_extnumoccboost.tbl or mode: w

You can resolve the problem by removing the incorrect rank profile (in the example incorrectly named "<test>":

$rp = Get-FASTSearchMetadataRankProfile -Name "<test>"
$rp.Delete()

Note: Do not modify the internal index schema representation (deployment-ready-index-profile.xml)!

See also http://support.microsoft.com/kb/2468431