Several certificates require an Intermediate Certificate. You will receive this Intermediate Certificate with your CA certificate. You have to install this Intermediate Certificate first! 

This applies (among others) to the following certificates: 

• GlobalSign DomainSSL - GlobalSignDomainValidationCA.cer
• GlobalSign OrganisationSSL - GlobalSignOrganizationValidationCA.cer
• GlobalSign ExtendedSSL - GlobalSignExtendedValidationCA.cer
• Thawte SSL123 - ThawteDVSSLCA.cer
• Thawte Webserver - ThawteSSLCA.cer
• Thawte EV - thawteExtendedValidationSSLCA.cer
• Symantec EV - SymantecClass3ExtendedValidationSSLSGCCA.cer
• GeoTrust DV - GeoTrustDVSSLCA.cer
• GeoTrust OV - GeoTrustSSLCA.cer
• GeoTrust EV - GeoTrustExtendedValidationSSLCA.cer
• GeoTrust SSL Certificates - RapidSSLca.cer

Installation procedure in five steps.

Step 1

Click Start > Run and type mmc. Click File > Add/Remove Snap in. Select Add.

Step 2

Go to tab Standalone, select Certificates and click Add.

Step 3

Select the option Computer account and click Next.

Step 4

Select Local Computer, click Finish and return to the MMC.

Step 5

Right-click  Intermediate Certification Authorities > All Tasks > Import

Complete the Wizard and select the Intermediate Certificate.

When finished, check if the Intermediate Certificate is listed under Intermediate Certification Authorities.