It clearly means that your proxy certificate is expired :)

Proxies are certificates signed by the user, or by another proxy, that do not require a password to submit a GRID job. They are intended for short-term use, when the user is submitting many jobs to the GRID and cannot be troubled to repeat his password for every one of them. The subject of a proxy certificate is the same as the subject of the certificate that signed it, with /CN=proxy added to the name. The gatekeeper will accept any job requests submitted by the user, as well as any proxies he has created.

Proxies provide a convenient alternative to constantly entering passwords, but are also less secure than the user's normal security credential. Therefore, they should always be user-readable only, with short period, and should be deleted after they are no longer needed (or after they expire).

The MyProxy is an online credential repository that provides secure and convenient storage for grid security credentials.

MyProxy is mature, open source software for the Globus Toolkit that has been used by the [...]

If you install your Terradue's certificate in your favorite browser you can be automatically recognized by the Terradue's Portal, Trac and svn. For this, you just have to install your personal Terradue's certificate in your favorite Internet browser and present it when logging in.
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The open source Globus Toolkit is a fundamental enabling technology for the "Grid," letting people share computing power, databases, and other tools securely online across corporate, institutional, and geographic boundaries without sacrificing local autonomy. The toolkit includes software services and lib [...]

The primary motivations behind the Grid Security Infrastructure are:

• The need for secure communication (authenticated and perhaps confidential) between elements of a computational Grid.
• The need to support security across organizational boundaries, thus prohib [...]

A gridftp server doesn't require any particular hardware configuration as the only service needed has not a big impact on the machine itself but only on the network traffic. Ideally such server has large disks and a gigabit eth card, but whatever machine can be used: larger t [...]

Please contact Terradue's Certificate Authority (ca at terradue.com) stating the project or collaboration you are involved, what are the current components that you need to use and your contact details. Generally generating new certificate takes some working days for identity confirmatio [...]