oops problem during request (4 replies)

Hello all,
After installing piwik and import a year data of IIS log files (using the python import script),
while opening piwik the data is shown for today but when trying to apply historical date I get
"oops problem during request".
This happens inconsistently, for few days I can see data for almost all I cannot.
I can always see data for today and yesterday so far.

"oops problem during request" always happens if I choose date range (week, month etc).

Moreover piwik is v e r y s l o w.

I have tried some suggested solutions I found while searching the problem, none worked.

My configuration is:
Windows 2003 server service pack 2
IIS 6
PHP 5.4.0
piwik 2.4.1


Any help would be appreciated.

Yotam