There can be a number of reasons why the IMA Service appears not to have started including the following:

IMA Service load time
IMA Service subsystem
Missing Temp directory
Print spooler service
ODBC configuration
Roaming Profile

Examine the following Windows Registry setting:
HKEY_LOCAL_MACHINESOFTWARECitrixIMARuntimeCurrentlyLoadingPlugin

If there is no value specified in the CurrentlyLoadingPlugin portion of the above Windows Registry entry then either the IMA Service could not connect to the data store or the local host cache is missing or corrupt.

If a CurrentlyLoadingPlugin value is specified the IMA Service made a connection to the data store and the value displayed is the name of the IMA Service subsystem that failed to load.

Missing Temp Directory

If administrators see an “IMA Service Failed†error message with an error code of 2147483649 when starting the MetaFrame XP Presentation Server the local system account might be missing a Temp directory which is required for the IMA Service to run.

To gain further insight into the situation change the IMA Service startup account to the local administrator and restart the server. If the IMA Service is successful in starting under the local administrator’s account then it is likely that a missing Temp directory for the local system account is causing the situation.

If the Temp directory is not present then manually create one as >Temp. For example:
C:WinntTemp