Windows server 2003 :No domain server available to validate your password

Am running on Windows server 2003 & the Domain Function Level is set to Windows 2000 Native. which means i can’t have Windows NT as a DC in this domain.

but, does this also mean i cannot have Win 98 as a client in the domain thatz running in windows 2000 Native mode. i had about 20 users logging into this Windows Server 2003 Domain from their win 98 machines. but now after about 20days win 98 machines are not logging into the domain. i get an error
” No domain server available to validate your password. You may not be able to gain access to some resources” when i try logging into the domain. i was able to login to this domain all these days.

i have removed all the patches, but the problem still persists. whatz the soultion for this.