Exchange Account-Unable to VerifyIncorrect Password iPhone

Since updating to iOS4.3 my work email on Exchange account no longer works (I think it worked for a day or so after the update but then stopped).
When I try to view inbox it states incorrect username/password and if I enter correct password it still says it is wrong.
If I try to change password in the account settings it then states Unable to Verify Account information. I deleted the account and tried to add it again and get the same error.
Someone else at work uses their iphone 3gs to access work emails on the same exchange account, and has no issues.
I can only find really old posts relating to this online, and nothing more recent, and am yet to find any solid reasons/fixes. can anyone assist/anyone else with exchange issues?!
This issue is the same on both my iPhone and iPad.
3GS & iPad iOS 4