I've seen a few of these problems lately where a user clicks on a link in PWA that should open a timesheet, a resource, etc., and instead, the user is rewarded with an "Error on page" in the lower left hand corner of IE.
In one case, we deleted temporary internet files using Tools > Internet options and that had no effect. So we deleted the contents of this folder on the file system in C:\Users\<username>\AppData\Local\Microsoft\Windows\Temporary Internet Files and that prevented the problem.
In the other case, we ran a repair on Microsoft Office Professional 2010. Below are my notes from the call:
On user's workstation, User accesses PWA > Server Settings > Manager Users.
He searches on a single user and attempts to click on the user's name to open the resource for editing.
Nothing happens except an Error on page in the lower lefthand corner.
'g_oFormPOst' is null or not an object
Logged into different workstation.
Signed into PWA, did same steps to repro and was unable to, so problem is on user's workstation.
Research indicates a repair of Microsoft Office will correct this issue; also clearing IE cache is an option.
Deleted IE cache via Tools > Internet Options.
Closed IE, reopened. Repro is still possible.
Opened Control Panel > Programs and Features.
Right clicked Microsoft Office Professional 2010 > Change > Repair.
Allowed repair to complete.
User restarted workstation.
Repair fixed the issue; unable to repro the problem.